"It is 100 per cent about the money," a family member said.
The targeted brother and the woman he is accused of abusing as a child told the Herald on Sunday the accusations are false.
They have each made statements to police and the alleged victim has been to the homes where the letters were dropped to tell people the accusations are false.
"I don't know how [the accused] is going to live in the area he lives in because of this," the woman told the Herald on Sunday.
"I have door-knocked the neighbours to tell them but I don't know where else he has gone so I don't know where to go next to help him."
The man targeted by the leaflet drop said he was "broken" by his brother's alleged actions and swears there is no basis to them.
"I hope that people realise it is not true.
"What he is doing … he shouldn't be allowed to do this. It is destroying me."
Neighbours spoken to by the Herald on Sunday said they were shocked to receive the envelope.
"It was good to get assurance it wasn't true."
The accused brother is the executor of the parents' will.
"He has decided to make a play because of the will. I'm an executor of their will and that has been the case for a long time but my parents are getting older," the man said.
The family is seeking a restraining order against the accuser.
"The police are really taking this seriously. He put it down at one of the local clubs but they looked at it and realised it was not right," the accused man said.
It is understood police have contacted schools to tell them there was no basis to the claims.
A police spokesperson said police would not usually say if an individual was under police investigation.
"However we can confirm that police are currently investigating a criminal harassment complaint."
"There is no further comment at this time while inquiries are ongoing."
Attempts to contact the man who did the leaflet drop were unsuccessful.
