I need some advice ,help 😭

The father of my kids , whom I’ve been with for 7 years I guess has been touching my friend on her butt a few times here and there ,here’s a run down I had a sister who past away last year while she was in the hospital , I guess that’s where it started , then I got into a really big fight with my friend and hadn’t talked to her for about almost a year but she started to come around more and she said he has been touching her on her butt again but at first she thought maybe it’s just an accident but then now it’s pretty frequent every time she come over . I’ve confronted him about and he keep denying it ,mind you I’ve notice something’s were it’s made me suspicious even before she had told me ! What do I do ?