He was a boy, she was a girl — can I make it any more obvious?

Oh, and he's also a billionaire heir.

Pioneering Canadian punk icon Avril Lavigne has quietly started dating Phillip Sarofim, the son of Egyptian-born Texas billionaire Fayez Sarofim, according to E! News. His mother was Mr Sarofim's second wife, Linda Hicks, who died climbing Mt Kilimanjaro in 2000.

The Hello Kitty hitmaker and her new billionaire beau have been seeing each other for three to four months, E! reports.

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Phillip's father is reportedly worth $US1.48 billion ($A1.95 billion), and as one of five children, he is an heir to that fortune.

Fayez Sarofim is the second largest shareholder in US energy infrastructure company Kinder Morgan and also owns a stake of the Houston Texans NFL team.

This new billionaire heir boyfriend marks a change of tastes for Lavigne, who has previously been married to Sum 41 frontman Deryck Whibley from 2006 to 2010 and Nickelback's Chad Kroeger from 2013 to 2015. She most recently dated prolific pop music producer J.R. Rotem in late 2017.

The singer has largely stayed out of the public eye since the release of her most recent album in 2013, battling health problems that left her bedridden for months and unable to eat.

"Why don't you try to get out of bed Avril, and just play the piano? Are you depressed?" a tearful Lavigne told Good Morning America in 2015 during her first on-camera interview discussing her battle with a severe case of Lyme disease.

"I was in Los Angeles, literally, like the worst time in my life and I was seeing, like, every specialist and literally, the top doctors, and they were so stupid, and they would pull up their computer and be like 'chronic fatigue syndrome'," the singer said.

"This is what they do to a lot of people who have Lyme disease. They don't have an answer for them so they tell them, like, 'You're crazy.'"

Last year Lavigne made headlines when a bizarre fan theory posited that she had in fact died in 2003 and had been replaced with a lookalike.