Re: Pets.
I don't think Kaidan would be a dog person. Select breeds, maybe, but as a whole I see dogs as requiring too much attention for his personality. He might try, but he'd likely be overwhelmed.
Tank and terrarium critters would be better. I think he'd like something he had to feed regularly and could derive enjoyment from watching rather than interacting with. The hamster or the fish would probably be good candidates for that type of critter.
Cats could strike a balance: he'd feed it and maintain it, and it'd do it's own thing, but every once in a while it'd come up and curl on his lap and he'd feel he done good because it likes him. (Granted, that's if he got the right cat).
Then again, while I don't see him as being put off by animals like some people are, I don't see him as seeking one out for companionship either, particularly in his line of work.
Re: Romances
I tried the new romances, expecting that I'd be hooked like I was with Kaidan, but got put off by the way they were handled and never went with any (no Paramour achievement for me...). I was expecting the slow, gradual buildup like in ME1 that felt very natural to me, and the ME2 romances... aren't, really.
Then again, the ME2 LI's have been with Shepard for over a year, so I'm sure they've had time to build now.
Also, I found this Kaidan.

Enjoy.