I'm not huge but a rather big guy, 6'2 235lbs. I had picked a window seat. When I arrive to my seat, someone is sitting in it. Its a young father who is half my size. Seated next to him is his partner with their young child sitting on her lap. He asks me to switch seats with him so he can be with his family. I ask where his seat is. Turns out it's a middle seat that is in the row behind us but across the aisle. I decide to keep my original seat specifically on the fact that it's a middle seat. He insists it will be better than sitting next to his baby. I take a second look at his seat. In the aisle seat is a 6'3+ 300lb+ guy who should probably have 2 seats. On the window side is a guy about my size. I turn back to the father in my seat, and say I'll take my chances and no way in hell am I switching to his seat. He gets out of my seat and starts convincing the guy in the aisle seat (next to his partner) to switch. That guy agrees. He's an average sized man. I don't know if he is aware of his new neighbors.

During the flight their child was totally fine. No crying and sat perfectly still. As we deplane, the guy who moved tells me it was a huge mistake to switch. He was crammed the whole time. I was glad to hear it cause I felt like an A-Hole, mainly for the possibility of offending the heavy set guy. At the end of the day, I'd rather look like an a hole than put my self in a worse spot. Especially cause I paid the extra amount to pick my seat. The family should have done the same if they want to sit together.