Deep sadness after my parents left for a week. Advice?

My parents left to the mountains for a week, with my younger brother in tow. They are all very close and I'm the odd one out who doesn’t know how to participate in this love fest. They rope me in sometimes, but it's all so awkward. I try to make jokes or do things, but it always falls flat. They want me to go to the mountains but I'd rather stay home with the dogs and watch TV. I don't want to spend 5 hours in the car and then pretend to have a good time. I can feel the pain and hurt in my heart, I miss what I think I used to have. I don't know how to feel or what to do. I'm 26 and this doesn't feel right. I want to go home I guess but I don't know where that is.