Help?! big dilemma. my mates brother?!??!?!?!?!?

Ok so i went round my friends house last week and went in her jaccuzi. It was so fun! Her older brother came in with us, she got out later on.. So me and her brother ( 15 nearly 16 ) were in the jacuzzi together. ( friends ) We were messing about and generally having a laugh... Then i went on webcam to her brother a few days later and he asked me to take my top off, seriously. Im thirteen years old and hes asking me to do that?! iv told my mum and dad?! I dunno what else to do?! xx