TRIGGER WARNING: This story discusses experiences of childhood sexual abuse, incest and suicide.
"I am very sorry I brought you so much pain," Marcus* wrote in his final letter, "Thank you for caring for me. I know I didn't deserve it."
Marcus died by suicide two years ago and when he did, he left University of Canberra researcher Lucetta Thomas a message.
The sentence that stayed with her was this one: "The only course of action is for you to do something positive, like finish the PhD."
To an outsider, these could be understood as simple words of encouragement. Lucetta knew their real meaning; this was an urgent final plea.
The PhD she's currently writing is about sons who were sexually abused by their biological mothers - just as Marcus had been.
Since she met him, Lucetta had witnessed Marcus struggling to come to terms with what happened to him in childhood.
"He was not only sexually abused by his mother from a very young age but when he became older and was able to physically prevent her from abusing him, she engaged another friend to be her strong arm so she could continue the acts of sexual violence against him," Lucetta explains.
"When Marcus died, I knew I had to finish the research. I didn't want this to happen to anyone else. I wanted these men to know they aren't alone and it's not their fault. There is help out there," she says.
It turns out Marcus is far from alone. For Lucetta's study, 94 men who had been abused by their mothers filled out online surveys. Of that number, she then interviewed 23 men at length over the phone.
"The abuse often started before the child hit puberty, when the child was still quite young, so they had really no concept of what was going on but they were still being coerced or manipulated into performing sexual acts," she says.
While some boys were mentally coerced into "a full sexual relationship" with their mother, Lucetta explains that others were on the receiving end of "incredible violence" if they tried to resist. Mothers might also withdraw of basic human needs, such as food and shelter.
Hamish,* now in his 50s, was 12 years old the first time he recalls having sex with his mother.
"She had this big bedroom and if we were ever sick or anything like that we'd stay in her bed. One day she just initiated it, she just started touching me and it just went from there.
"She preyed on the fact I was coming into puberty and made me feel important and special," he tells me.
From this distance Hamish now understands he was just a child when the abuse occurred; he was unable to consent to sex with an adult in a position of power.
At the time though, it was a different story: "I thought I was enjoying it and I thought I was grown up."
Despite growing up in a wealthy suburb and going to a private school, home life was difficult. His single mother suffered frequent physical illnesses, such as pneumonia and pleurisy. In retrospect Hamish thinks his mother was also mentally unwell.
"It was a good household to be in when my mother was in a good mood and it was a horrible household to be in when she wasn't," he says. "She would threaten to kill us and she'd lock all the windows and turn on the gas."
"I got hurt," Hamish continues, pointing to a decades-old scar on his the top of his head.
Especially when his mother was sick, Hamish cooked, cleaned and went to the shops to get food for the family.
"She saw me as like some sort of de facto relationship, I've got no doubt about that. She'd say: 'You're the man of the house'," he recalls.
Meanwhile his mother warned him to stay quiet about their sexual relationship.
"People wouldn't understand, you can't ever tell anybody," she told Hamish.
The truth is that Hamish had no one to disclose the abuse to - and even if he did, was terrified of splitting up his family.
"You're physically and mentally trapped in this relationship and you can't get out of it," he says.
This isn't an easy interview. When I ask what went through his head during that period in his childhood, Hamish struggles to form an answer. Like so many men in his position, the distress lies not in the words but in the silence.
"[I've] spent most of my life trying to repress these thoughts and memories," he says, "I haven't talked to anyone for 30 years about it."
When he was just 15, Hamish's mother died. While making it clear he didn't wish for her death, Hamish is blunt: "She did me a favour ... I've always felt that it enabled me, in some respects, to get on with my life."
He worked hard to do just that. Hamish married in the early 90s and fathered two sons of whom he's extremely proud.
About 10 years ago a television news story prompted him to briefly mention the childhood sexual abuse to his wife. After the disclosure he promptly told her: "I never want to talk about it ever again, ever."
Quietly reflecting on this, he says: "It's really hard to tell someone you love, 'By the way, my mother abused me and I had sex with my mother'."
True to his word, Hamish never did discuss it again with his wife - something he has lived to regret.
"I love my wife and for a lot of the time we had a good relationship but this thing [the abuse] came between us," Hamish says. "It did slowly poison our relationship."
"Our marriage was never the same after I told her about my mother ... just telling her wasn't enough. We needed to get help," he says.
Three years ago Hamish had an affair and his marriage unravelled. As a result he lost his wife and his business.
"I wish we'd got help together, you know? I might still be married now if I'd got help. But I'm not," he says with unmistakeable grief.
Despite this, Hamish no longer feels anger when it comes to his mother.
"I feel sorry for her that she couldn't see what she was doing was wrong," he says.
It's an incredibly confusing situation for victims, explains Lucetta, because "the boys still love their mother" and just like Hamish, "they don't want the family to break apart."
Lucetta says men who were victims as boys are deterred from disclosing what happened due to the very real fear of not being believed or being blamed for their maternal abuse.
"Society says that males are actually instigators of any sort of sexual relationship, so the child copes with the trauma by telling himself: 'I must have actually instigated it,'" she says.
Lucetta recruited the men for her research with relative ease. This may lead one to assume this type of abuse is common. However, there seems to be no reliable data on its prevalence - including the Personal Safety Survey conducted by the Australian Bureau of Statistics.
The way Lucetta sees it, the lack of data leads to both a lack of public awareness and acceptance of mother-to-son sexual abuse and a lack of "support and assistance for these male victims by health professionals".
Ian,* 70, was also sexually abused by his mother. Unlike Hamish, it happened when he was a much younger child.
"I as a child felt all yucky about it," he recalls.
Up until the age of eight, Ian says he slept in his mother's bed and was asked to perform sexual acts on her.
"I hated her because of abuse," he says, "I had a list of people who I wanted dead and she was on that list."
The family dynamic was complicated. Ian, his two brothers, mother and her husband - we'll call him John - lived in poverty in rural South Australia.
"I was born illegitimately," Ian says, "and he [John] knew that because he wasn't sleeping with my mother.
"My whole life I felt guilt and shame because I shouldn't have been in existence," he says.
Growing up, Ian "just existed" rather than living. John kicked Ian's mother and her children out of the house several times.
"I was shunned, I wasn't wanted. I felt that even from my cousins, uncles and aunties, grandparents," Ian says.
For Ian, the childhood abuse "manipulated my sexuality and impacted my ability to operate as a person".
"How can you have a healthy sexual relationship? How can you become a father, husband, grandfather?" he asks.
Throughout adulthood, Ian has been plagued by feelings of isolation, guilt, low self-esteem, depression and anxiety. He's also battled a "dysfunctional sex life" and attempted suicide a number of times.
Ian describes "a paralysis" inside him and states: "I don't think I've loved anybody in my life [and] didn't know what love was."
Although Ian is still married to his wife and has been for nearly 50 years, he confesses to having a number of extramarital affairs and visiting escorts for sex.
Only in the last six years - and after decades of counselling and therapy - does Ian feel he's started to recover.
"I honestly believe she [his mother] had probably been sexually abused herself," he says, adding: "I feel pity for her."
"I had to forgive my late mother in order to recover," Ian explains.
In the context of Lucetta's research, Ian is unusual because he considers himself mentally healthy.
She says: "Out of all the males that I spoke to I would say only one had actually come to terms with what had happened to him."
The sexual abuse of "these men when boys is often highly traumatic and at times extremely violent and impacted on their psychological, biosocial and physical development," Lucetta says.
Far from healing over time, the impacts of this mother-to-son childhood sexual abuse seem to continue.
"There seemed to be a recurrence of the trauma building up over the years," she says, "so from the late 30s onwards, it was really starting to become an issue for them."
As adults, the majority of men in Lucetta's study felt "very trapped, very isolated, very afraid and very unsure of how to go about getting help and understanding the power dynamics that they had been subjected to".
"One gentleman, sadly, was completely house bound. He basically just felt that it was completely impossible to trust anybody or to be out in society because he had so little self-regard," she says.
According to Lucetta, society's beliefs about gender are effectively stopping a cohort of male victims disclosing their abuse and accessing support.
"They have experienced the same forms of trauma, the same forms of sexual abuse and emotional and psychological abuse as any victim of sexual abuse or sexual assault and they need to be taken seriously and they need to be believed.
"It is time to break the long-held view of mothers as only ever gentle and caring females, so that the sexual abuse of sons by their biological mother is acknowledged," she says.
For Hamish's part, he urges other survivors of mother to son abuse to reach out for help.
"You can't just bottle it up and think that it will go away, because it doesn't ever go away," he says. And he would know.
• Names and some personal details have been changed for privacy reasons.
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If it is an emergency and you feel like you or someone else is at risk, call 111.
Ginger Gorman is an award winning print and radio journalist, and a 2016 TEDx Canberra speaker. Follow her on Twitter @GingerGorman