You know... A lot of these posts make me super sad. I don't think it's ok to invite biological nieces/nephews or brothers/sisters and not invite step versions of those same ones. ESPECIALLY when they're kids.
Let me tell you all a little story. I was a stepkid and I had to spend a lot of my life figuring out what I could do to become "good enough" for my stepfamily. My parents divorced when I was 2 and were both remarried by the time I was 4. I had stepfamily all of my life. I could SEE the difference in how I was treated compared to my stepsisters/brothers and stepcousins. It's NOT fun.
If you're doing no-kids, that's one thing. If you're doing no-kids and then allowing nieces/nephews then that's fine, but to do no-kids and nieces/nephews but not inviting your step versions of that is just cruel to the kids. Try explaining to a 5 year old why their stepcousin was invited but you weren't. They are not going to understand any reasons about "closeness." continued in comments...