How can my family get back together?

In Oct. of 07, I was going to be a cowgirl and I needed a hat. My uncle and his family live in my grandparent's old house, because my grandma re-married and moved out after my grandpa ped away. My mom called over to my uncles house to see if I could wear my grandpa's cowboy hat and he was like "Well only if "I" get it back because it's mine" and my mom flipped. They got into this huge arguement about how everything in that house is as much my mom's as it is his.B/c, I mean he basically got everything (house, car, all of my gpa's belongings.) Their phone call ended with "Well I'm not coming over to get the hat" and his reply was "well good because you are NOT welcome here." She was also mad at my gma bc she didn't do anything, but they made up a week later. My mom and my uncle and aunt aren't talking at all. I thought it would only last for a week or so, but I went through C-mas and Thanksgiving like this. My mom said they aren't invited to my sisters highschool graduation!