An accusation of inappropriate touching?

okay i have a close friend whom ive known for over 20 years. he has 3 kids, 1 with his new wife and 2 older kids with his ex-wife. he had to give physical custody of the 2 older kids to the ex because he lost his job and home and had to move far away. he had a rough divorce and his ex is a seriously messed up, sick woman. he just saw them a few weeks ago and they looked horrible in the mothers care. then all the sudden last week his older daughter who is 12 supposedly told her mom that 2-3 years ago she was touched in some manner inappropriately by him in some manner. cps and detectives did an investigation and found the other 2 younger kids were fine. but the mother wont let either of his kids talk to him or any member of the family. the police nor cps never advised the ex to do this either. now they want to question him next weekend and then possibly submit the report to a prosecutor for review. this 12 year old has had a history of stealing and lying numerous times.