Need to move ASAP!

I’m so freaking tired of this! Why is it our responsibility to watch my bfs niece when we didn’t sign up for it. His sister won’t grow up and take care of her own daughter so his mom has to (we live with his mom). But she works so when she works on the weekends we literally have no choice but to watch her. It’s not fair. I have my own son to take care of which I find difficult enough. Everybody is getting mad at me because I express how difficult it is for me to take care of both kids. His niece doesn’t listen to me very well and she has no form of discipline. She tries to bully everybody including my 1 1/2 year old. Unfortunately we don’t have the money to move.