Successful breeding of Pets?

I've have been trying to make two dogs breed pretty much from the day the pack released and had absolutely no joy - every time they were encouraged to breed they would growl at each other and the owner would get the sad moodlet. I had different members of the household encourage them, I moved the household out, deleted the house, replaced it and moved them back in, repaired the game and still nothing. Finally I snapped and adopted another male dog (because I really want to breed from this particular female) and directed her to breed with him minutes after he was adopted. She did first time, and is now pregnant.

I guess some dogs just really, really hate each other.