On international or cross country flights with my brother (who is a 1K), since we both like window seats, I will just book 2 window seats. I also monitor the seat assignments to try to get as close to an empty full row as possible. On our last flight to China, I had the most comfortable flight, slept 8-9 hours across 3 seats in coach (and still had time to watch a movie and eat). Woke up with almost no jetlag. My brother and I don't feel the need to sit next to each other, and since he was in the row in front of me, I could still talk to him if I wanted to.