Is it common for a male and female cat to be lifetime mates?
No, not unless they are brought up together with a family. My cat Molly has what I lovingly call "friends" and the same cats are around and since she has been spayed I have no fear of her becoming pregnant. I watch the cats simply play by the trees and in the ferns in the backyard and sometimes they get into the odd slight feisty scrap, but are friends ago. Sounds much like human nature doesn't it!