PLEASE, I NEED ADVICE

My husband and I have 4 kids. 2 girls and 2 boys. Girls are 13 and 8. Boys are 13 and 10. My daughter told me her 13 year old brother grabbed her butt and later told her not to tell me or else she wouldn’t be getting a toy she’s been asking for. A few

Months ago 13 year old sister said brother grabbed her butt while she was asleep and he said he was trying to find a toy in the dark (sleeping in living room with cousins at the time) Said it was an honest “mistake”. This time Brother admitted what he did after trying to lie and said he grabbed her (8 year olds) “leg” and does not know why he did it. Says he’d never sexually touch her but sister felt very uncomfortable and we’re trying to fix this. But what do we fix? Does he get counseling ? Is he going to grow up to be a “weirdo” or grow up and try to rape someone ? What do I do ?