If it helps, I can give you my story:-
I discovered that some couples enjoyed bringing other men into their relationship physically pretty early on in my teens, I didn't really meet any couples until in my 30's, as had plenty of opportunities with single women, but often fantasised about it, and enjoyed looking at contact magazines etc. as part of that. I guess i've always been interested in real women, often older, and the 'wife next door with a naughty side', so this played into this.
As I got older, I discovered I actually really enjoyed being watched, and started meeting couples where I could from a few swinging sites ( hard as one of many single men) but typically for more longer-term, as I found I enjoyed chatting to hubby as well, and the build up to a meet.
Through this I discovered the more 'cuckold' lifestyle, it's preferences, and came to discover to my pleasant surprise that I really enjoyed a more submissive man being interested in me, his wife, and the three of us. I met a wonderful couple from a similar site no longer online, who I was a bull for, for some time.
The main reason I took a break from meeting my couple, was I met a single woman desperate to have a baby before she got too old. She was going to find a donor, and try to go through IVF alone having been told she was almost infertile.
I got her pregnant the first time I filled her full of my cum 🤣, and tbh was happy to stick around although there was no obligation. Circumstances meant my couple, and I lost touch but It did make me think about how I would have felt had it been another man's wife I impregnated, and frankly the only thing I regret is she wasn't someone elses wife, with him holding her legs open for me to breed regularly. In retrospect that would have been perfect.
So I'd say there are genuinely couples out there desperate to have a baby, where he is not up to the task, and men happy to provide what is needed, as part of a grown-up adult relationship...I know, I'm one of them 👍