Assuming you didn't let anyone die and recruited all the available first-gen characters, I think there's always at least one guy extra than there are eligible women to have kids with. So some of the poor guys don't get anyone and are forever alone bachelors.
For mine, it came down to Stahl. He was the only guy not to get married. He's just too average, so I had Donny marry the last girl. Poor Stahl. :(
In my first playthrough Ricken and Kellam were forever alone, but mostly because I forgot they existed. And I had a male MU so I naturally took one of the girls. --- Behind this username there is more than flesh. Behind this username is an idea. And Ideas Are Flame Proof.