AITA my (21m) parents asked me to babysit my sister (5f) during spring break

I am in college and came down to visit my parents for spring break but they had me babysit my little sister the whole day instead of spending time with me (I was only there for 3 days and played with her most of the time). I told them I didn’t come down just to babysit and they got angry because they think it’s what I should do as an older brother and part of the family. AITA for thinking this isn’t my responsibility?