LOL, this is a great question for me. Yes, been there, but the SO adjusted, very well might I add

. My dh and I have been together for almost 8 yrs., married for almost 1yr

and living together for 7yrs. When we first moved in together, he didn't want my Beagle (who was about 5 at the time and I've had since she was 8 weeks). Well, I said "That's my dog, she's MY responsibility and she WILL live with me till the day she dies. I had this dog WAY before I had you!" LOL, long story short, he learned VERY quickly how much I love animals and we now have 5 pets lol.
He didn't want either of the cats (supposably he's not a "cat person") but where can you find him every time he goes to bed - petting our cat Summer and "baby talking" to her, telling her she's a "good kitty" LOL. He taught our cat Chooch how to fetch too. He also was against me getting Alice, but he pets her all the time, even lets her lick his face. I wouldn't say he LOVES them as much as I do, but he definatly does more than just "tolerate" them. That would have been a deal breaker for me, yes.