I have this villager who for some reason, just can't father children.
I tried pairing him up with a bunch of different girls, and nothing. I even had him "married" to a female, and eventually I had to get them "divorced," and have her "remarry" because I really wanted her to have a baby.

The funny thing is, now he goes around trying to mate with all the girls. They still can't get preganant, and most of them just run away! LOL

Just out of curiosity, does he have any dislikes displayed on his details screen?

No, he doesn't.
I notice the only thing he seems to really stick with is Researching, though.

The villagers do exhibit different personalities. Why don't you let him research for awhile and then try again when you have different females for him to meet.

Yeah, that's cool. Maybe he's just needs "the" female to come along.

I have one adept parent that will only mate with one of my adept farmers... I didn't think that he will ever become a master because my adept parent is a female over 50, so right after they come out of the shack, they embrace again and go back in.... it's prety funny. I even picked him up and put him up by the gong and she still ran up to him. I finally switched her preference over to research and that seems to keep the embracing down to once in a while!

Yes, it's much easier to make good parents after 50.

actually kjlittle if you want him to become a master you should the two of them stay together - he'll master it "the safe way" unless you want more kids