I've not rtft just giving my 2p.
I understand completely how you must be feeling. It's an exciting time, first baby who you have waited a while for, and probably not many people know about the pregnancy so not many people to share with. And to some people, developmental stages are interesting. I found it fascinating to read that something so tiny had ears, toes etc. Also, we had to have early scans, so seeing the heartbeat at 7 weeks was a relief that our parents were very happy to hear about. So in the sense that you are upset you can't talk about this, YANBU.
However, for any form of pregnancy loss, self inflicted or not, a year is not a long time and I wouldn't expect anyone to be over it. (Perhaps not ever) Nor would I necessarily expect them to be happy for you - though of course it would be kind for them to try and rise above those feelings in your presence and at least feign happiness.
It is not your fault that they were not in a position to have a baby, and is unfair that your baby isn't being celebrated as much as it would be otherwise.
I can though completely see how hard it would be to sit and hear that baby has (for instance) a heartbeat at potentially an earlier gestation than the baby they aborted. It would bring back many memories.
Unfortunately I can't offer a solution. Perhaps apologise to your DB for unintentionally causing pain, and tell him what your parents have suggested and see what he says? I would also tell your parents how much this has hurt you, and you wish you could have some time with just them to freely talk about the baby. I would also ask how long this embargo on pregnancy talk will last.
Congratulations on baby. If you haven't already, join a due date group on here or another forum, they are very useful x