I don't know where to confess my sins anymore so I guess I'll do it in this thread

A few months back, I would sneak into my little sister's room and do stuff with her... just little things, like kiss her and touch her places, and one time I wiped a tiny bit of cum onto her feet. Nothing that serious, nothing that would hurt her.

I only did it maybe 10-15 times, and then I stopped, but my sister and mum have been acting strangely for the past week or so, and two nights ago, I overheard my mum asking questions to someone over the phone that were pretty obviously related to what I did with my sister.

I immediately packed my bag and prepared to GTFO town as fast as fucking possible, only for my mum to confront me and tell me about what "your father" was doing to my sister, and talked about the possibility of telling the police. Apparently my sister thought it was my dad doing it, and brought it up in casual conversation with my mum, which is how she found out.

My dad has previous sex offenses (none of them actually that serious), so this might just fly.

Is there any chance they could get DNA off of her feet, and if it did, wouldn't it test as a match for my dad since we're both closely related?

I'm also kinda worried that maybe my mum is lying to me or fucking with me and knows that it was me all along.