So I (f20) older sister (f28) boyfriend (m27) bought my one of two of my sister (f27) dog we named him Marco. Anyways he bought Marco a month ago from my sister since she didn't want Marco cause he's hard to train. Which he isnt really. Anyways everything was good until yesterday when she found out I was moving out of state.

She told me to bring back "her dog" now since I'm abandoning her in a few months, I don't get her dog. The thing is Marco isnt mine. He's my sisters (f28) boyfriends dog. They both love each other. He already went to Michigan but is coming back in two weeks to visit before leaving for a month. He is planning on being Marco back to Michigan with him.

I told her to fuck off and that Marco isnt mine so I have literally no say in what my sisters boyfriend does with Marco. He literally loves Marco so much. My sister (f27) is mad at me for telling him that she wants Marco back. But I'm not gonna do that to someone I consider my brother. My sister (f27) boyfriend told me I had no right to bring him into this situation, I told him I had so many rights to bring him into this situation and that he can fuck off to. Now I got both of my parents telling me I need to do the right thing and give them back their dog. But I feel like they are manipulating me into trying to stay in Kansas. Both of my grandparents are also siding with my sister about giving her the dog back. I got my sister (f28) and her boyfriend and his family on my side saying they have no problem with him buying Marco until they knew I was going to leave.

So am I the asshole for telling my sister she can't have "her" dog back just because I'm moving out of state in a few months?

Edit: this all happened two hours ago and I'm still getting calls from family telling me I'm an asshole sorry for how I wrote it. I'm pissed off.

Sam wants me to give Marco back to her even tho he's not my dog I told her no and told Jack (Kay's boyfriend) about it since he payed to have Marco. She's now mad at me for 1. Telling Jack that she told me to give Marco back to her ASAP. 2. For refusing to give Marco back just because I'm moving out of state in a few months.