I'm in a happy, healthy and loving relationship with my boyfriend of a year and a half. We're both in our late 20s. Things are generally going great, but there is one thing that is really bugging me — both of his older sisters consistently give me the cold shoulder. They aren't rude, they just seem very disinterested, like they don't take me or our relationship very seriously. I'm pretty sure it largely has to do with the fact that my boyfriend was previously engaged to a girl he grew up with. She called off the wedding, but they had both been unhappy for quite some time so it was all for the best. He and I met and started dating a few months after they broke up and fell for each other really quickly. I've never once felt like his rebound — the love between us is very real and his friends (and our mutual friends) told me from early on that they had never seen him happier. But when I'm around his sisters my insecurities start to get the best of me — I start to feel uncomfortable and awkward and not very at home with his family.
He and his ex were together for seven years. She was close to his family. In no way did I expect to just step right into those shoes, and I feel like I've been very understanding of the situation and the fact that they might have been unsure about him being in another relationship at the start. But one and a half years in, I'm starting to get frustrated at the less than warm welcome. I get along great with his mom and step-dad, and his little nephew adores me. My family has been really warm and welcoming to him, my sister and her husband make every effort to include him and get to know him better. I've brought it up with my boyfriend and he said he never really though about it until I said something, but that he agreed with my analysis that they just seem somewhat disinterested. He said they had never really asked about me (but being a guy he had never given it a second thought) and that he thought they probably just didn't trust him anymore when it came to relationships.
I get jealous when I see my friends and other family members who are close with their significant others' families. I know it could be much worse — and I know in the grand scheme of relationship issues this isn't a huge thing to complain about, but I'd love to find a way to make things better. Any advice?