Refusing Sister’s Last-Minute Babysitting Demands

AITA for refusing to babysit my sister’s kids after she said it’s my job? I’m twenty six,

no kids, and I work full time. My sister has three kids under ten and

constantly asks me to babysit last minute. Last week she texted me saying she needed

me to watch them again. I said no because I already had plans. She replied that

I’m family and that helping her is basically my responsibility since I don’t have kids of my own.

I told her I’m not free childcare and that her kids are her responsibility. Now my parents are

mad at me, my sister isn’t talking to me, and they’re saying I’m selfish.

So… am I the asshole?