Ex girlfriend problem?

ok, so i dated this lovely chick for about a year, and we broke up around december of last yr. we still talked and told each other that we think about each other alot, and wed hang out and mess around, but we wouldnt sleep together, which was frustrating to me bec it was mixed signals and i was getting confused. i have had a good relationship w/ her family, so me and her brother we still hang out sometimes, and w/ how things have been between us ive been mainly hanging out w/ him and w/ her i have been saying no, and well thru out the yr i was w/ her her brother never got in between us ever,but tonight he did, he asked me to hang out w/ him and told me his sister was there so i said no ur sister is with u id rather not, but he tried to force the issue by asking why when he has never done that, bec i dont know what his sister wants from me, and i dont wanna get hung up on her again if she is trying to mess w/ my mind, im so confused and dont know what to do.