It's very strange, my significant other's jealousy. Sometimes he gets jealous, sometimes he doesn't care. Depends on his mood, maybe.
Actually, upon thinking about it now, I think he does get jealous but tries to appear nonchalant. He told me upfront awhile ago that he wasn't a jealous person, but he has shown some jealous/possessive behavior (which is fine by me as long as it's not overbearing).
Note, he also said upfront awhile ago that he wasn't a breast guy, and he adores my boobs.