I'm not sure how to bring this up. My sister has a tendency to come over, and gives the impression that it will be a quick trip of about an hour, but instead takes 4 -5 hours. She leaves her kids unattended, assuming I or my mom should take care of them, and then does whatever she needs to do at the time.

Both her and her husband do this consistently and her kids will actually start begging to go home if they do this late in the evening, but they won't go home.

Any time they come over they never attend to their children. The rest of the family has to mind them. I understand that parents need a break and relax, but it's 100% of time when they come over.

I like my nieces and nephews, but I don't want to clear my day to babysit. I'm not a parent. I don't want to be a surrogate parent. I am aware that the children like me less, because I'm the one that has to say "don't do that" or "stop that" or "Don't put your hands in your food." or "Pick your nose in private."

She takes things super personally and will see this as me saying "I HATE YOUR KIDS AND YOU" but it's really "Please stop being so inconsiderate, I'm not a baby sitting service. Respect that I also wanted to do things today."

I'm also the youngest, and I have no children, so there's always "BUT YOU DON'T UNDERSTAND WHAT IT'S LIKE." And my father will 100% take my sister's side because she's his princess and I look too much like my mother which makes me evil.

Sooooo how do I breach this topic without her stabbing me in the feelings?

ETA: Thanks for the advice ^_^. I will work on boundaries. I am so not good at them.