Is it normal that i hate being an aunt?

I hate being an aunt.I never asked for this and I'm sick of having obligations tied to my nieces. If I had actual say in the matter, I wouldn't be an aunt. I'm uncomfortable around my nieces (I look forward to when they go home) and I'm sick of the responsibility. Why should I help their grandma (my mom) with them when she herself had FOUR children? She has much more experience at this than I EVER will. If she wants someone to help her with her granddaughters so bad then why doesn't she ask someone who's an ACTUAL child minder instead of someone like me who will NEVER have kids? You'd think the actual parent with lots of experience would be a far better choice than me. She doesn't ask my twin brother to watch them as much as she does me. WTF? Oh, I get it. It's because I'm female and child-free isn't it and Mom expects me to be the "Ready and Eager" babysitting aunt. All I can say is this: If I wanted to be a Baby Sitter and deal with kids so much, then I'd be one of the following: Daycare Worker, Teacher, Babysitter, Nanny, or Mother (Biological and/or Adoptive). But because I'm none of these things: Stop getting ME to watch them. I may love my nieces, but I feel like it's only out of obligation and if I had had my way, I would've never became an aunt and I never would be one.