AITA for Not Wanting to Babysit My Sister’s Kids Every Weekend?

I (24F) am child-free and live alone. My sister “Emma” (30F) has three kids under the age of 7, and while I love them, I’ve always made it clear that I’m not interested in babysitting regularly.

Recently, Emma and her husband have been asking me to babysit almost every weekend so they can “have a break” or go out on dates. I’ve said yes a few times, but it’s becoming a regular expectation. Last weekend, I told her I couldn’t do it because I already had plans, and she got really upset, saying I wasn’t being supportive of her as a mom.

She argued that since I don’t have kids, I should have more flexibility and that helping her out once a week isn’t a big ask. I told her that while I don’t mind occasionally babysitting, it’s not my responsibility to sacrifice my weekends for her. Now she’s been distant and has even told our mom that I’m being selfish.

My mom thinks I should “help family out” and that I’m in the wrong for saying no. But I don’t think it’s fair to expect me to give up my free time every weekend. AITA?