Are the NPCs off-limits?  The only decent looking townie I've found is a repair(wo)man and despite having the "extremely irresistible" message, there's no option to ask her to go steady or get engaged or anything?  Both are single.

My sim just had triplets.  Both she and the father had the fertility perk.  I don't know if you'll be able to get triplets without it but that's how I did it.

Also, I noticed that if you go to the hospital, it randomizes one trait and you choose the other.  If you choose to stay home, it'll randomize both.