My ds3 just turned 7 yrs old. Last night he slept round my sisters house which he was very excited about. My sister has 2 dd 18 mo and 5 yrs old. My 5 yr old niece and my son play happily together and my son is a very caring loving child. However when my sister bought him back to me this morn she said that there was an incident last night whilst my ds3 and my niece were playing upstairs and that my ds3 had put his hand down my nieces knickers and touched her 'bits' and she said that its not the first time it had happened that it happened once before. My sister is really upset and was in tears about it. I'm distraught that he has done this and why? I have talked to him about it and how we mustn't touch any one else's private parts and or show anybody our 'bits' but he knows this wrong already and was really upset when I was talking to him about it because he knew it was wrong but couldn't give me an answer why he had done it.
He is the youngest of 5 and have 2 DS 15 yrs old and 13 yrs old and 2 DSS 16 yrs old and 13 yrs old although DSS don't live me and dh but stay once or twice a week.
I just want to no if this is something I should be worried about as I can't stop thinking about it as it something I've never come across before with any of the others.
Any advice ?? X