I know i'm not a man so I can't possibly hope to understand the emotions behind pregnancies from their perspective.
I also do get that some guys like sharing their partner, cuckoldry, swinging etc.... I've got friends in the swinging lifestyle who have explained it so I get that part.
My thing with not understand the whole pregnancy feeling for a man is, while I understand the kink of sharing your partner, finding out they are going to giving birth to another mans child has to be upsetting, no?
I mean, it's one thing to see your partner experience pleasure and get a thrill out of that but her giving birth to another mans child is huge. It ties his partner to another man for the rest of their lives. They will always share something deeper than he can offer. He can love her, she can love him but she brought life into the world with someone else. No matter how much he loves his partner and how much he enjoys the pleasure side of things, he'll be co parenting a child that will never be his. He'll only ever be the step father of a kid in his own family.
Like I said, I can totally understand the kink side of things but I just don't get the pregnancy side of the enjoyment.