Should I go?

My family and I got invited to go his friends house for new years.....but I dont know if I should go..I mean my dad friends daughter is like my bestfriend....but I almost wen tout with her brother but at the end didnt and ended up going out with their cousin..but we broke up a while ago....so should I go to their get together wih my family? I dont know...I think that I might feel wakward? please help! thanks..I am so confussed!