Thank you all so much for your comments and support!
I'm honestly surprised people actually read all of my rambling.
I finally sucked it up and asked OH to really tell me how he feels about this entire situation, what he wants to happen, etc. Normally he doesn't like talking about his thoughts if they're upset (he hates being in a bad mood!) but he surprised me by being completely honest. We had a long talk, and we've decided not to tell his family. If we end up changing our minds, we'll only tell them after the baby is born - visitations would be very limited. We are going to tell his twin brother, of course, after our three month mark. He'll be overseas, but I'm sure he'll be happy and supportive!
Chulie, thank you for everything! Both OH and I definitely agreed with everything you said. It's really disappointing they have such huge issues with the both of us, and OH has tried discussing how he feels with them countless times. His mom seems to think he's being dramatic about it, because "he knows how his dad is", and quite frankly his dad just really doesn't care. I don't speak with his family often, though when I do it's always with OH beside me. I'm a generally shy person anyway, and I just feel uncomfortable by myself with people I don't know regardless. :3 I'm most definitely "honey" rather than vinegar though! OH's grandparents and I get along really well now, but sadly his cousins (minus one, the only girl) and his parents just don't seem to care how hard I try. Thank you again, we're definitely making the most of it! OH said to me last night, "this is my family now, so I'm not even bothered anymore". It really means a lot!
Thank you again to everyone who responded! I was obviously very upset (and still am a bit) but I've calmed down and realized they just aren't worth me being angry. If anyone else wants to reply please feel free to do so! But really, thank you all again! All of your posts made me smile.