What do I do about these family members that bug the hell out of me?

they're my aunts family,she has 2 kids and she's married and they ruin all of my family's plans. i'm a kid so i go to school and i only have the weekend off every week, so the weekends are pretty important but they come along for diner so we have to change our plans and then on top of that they spend the night when they are perfectly able to go home but they don't and then the next day (Sunday) we go to Walmart, PS. I hate Walmart, and we spend 2 hours in there just to get toilet paper for them! O.K. It's already 4 o'clock and so we go home (my home) and then they spend the rest of the day there watching my t.v. and eating my food, then on top of that they decide to leave at my bed time (9 o'clock). They mooch off of us and that pisses me off. HELP ME!!!!!!!!!!!!!