Not sure what to do
I am a 14 year old girl and I baby sit on a regular basis for a family who live near me. They have two girls, aged 5 and 7, and a boy aged 12. The boy is ok until the young ones go to bed but then he starts doing and saying things of a sexual nature. At first he was just saying rude things, then he started to expose himself to me. Then the other night I came downstairs after putting the girls to bed and he was sat in the chair, in just his vest, and he started masturbating in front of me. No matter what I said he didn't stop, he just thought it was funny. On another occasion he urinated in front of me. I don't want to stop babysitting because I need the money, and I couldn't possibly discuss this with his parents, so I will just do my best to ignore it. I've talked with my friend about it and she just thinks it's funny too, in fact she's even said she'll babysit with me so that she can see him do it.