Kids keep touching me

I’m embarrassed to be saying this but I genuinely need advice. I’m 18 F and I recently started babysitting for this family, that has two young boys. They are loud, misbehave often and do not listen to anything I tell them to do. But worst of all the oldest (9) slaps my butt all the time, tackles me and seems to want to touch me inappropriately at times. First it starts off with him wanting to cuddle (in his bed) I thought that was kinda weird since I’m a stranger but then he starts humping my leg!? What!? So I tell him to stop and try to get away but he often pulls me back down. Also the younger brother (5) constantly wets himself and they both are extremely touchy. But I thought maybe i think it’s weird cause I grew up in a very distant family. Oh and they are always taking their clothes off in front of me and running around I think it’s odd. I don’t know how to bring this up to the parents or how to stop this behaviour and get them to listen to me. I’m a bad babysitter I know. Let me know if any of you have advice?