I'm supposed to visit my sister's family for thanksgiving this year, but I'm not really looking forward to it. We haven't gotten along over the past several years.
Sibling rivalries are unfortunate. Hopefully you two can patch things up one day?
Maybe. She has a lot of mental difficulties that makes it hard to be around her. Short visits are okay, but anything longer than that gets uncomfortable. 
Ah, i see. I hope you end up going and find a way to enjoy yourself. Family is all that matters in the end. 