The loner trait is kinda negative. I gave it to my Japanese guitarist, because I wanted him to be more shy, like many Tokyo guitarists tend to be. It worked. The poor guy gets very nervous and tense around strangers, even children. His best friend had twins, and when I have the toddlers click on him with "talk to stranger", the loner guitarist gets very uncomfortable. It took a long time for him to be comfortable around the toddlers! lol
I haven't tried the "hates children" one yet. I've been hesitating, because I want to breed my characters. But my brother made a girl who "try for baby" with the first npc that was interested, without bothering to learn the guys traits yet. She had triplets, so she invited him to move in with her. Only then did my brother discover that the new daddy "hates children".