this is hard and I hope writing it out helps

1) This is very hard. I understand where your sister is coming from, less the rest of your family. They are greiving the loss of a grandson and that never goes away. I don't know if you've tried writing to them, explaining you'd never deliberatley hurt anyone and you hope that they can welcome the new addition to the family, boy or girl. It may well be they never do and then I think you need to work through that at the time. It's hard I know, but try not to assume they'll stay negative. They may not. you know your family best - do they hold grudges?

It's not your baby's fault the timing hurts other member of the family. They need to know that. Meanwhile, can you surround yourself with friends who are excited for you, plan a blessingway, plan diplomatic baby announcements. Who will tell your sister and when, for example?

You need to work through the what ifs? What if your family dont accept the baby? What if he is a boy? He will still be loved, he will still be wanted, he will still be a precious gift. Obviously, avoid like a plague a name that resembles his deceased cousin. I wouldnt do that to a child anyway. I suppose I'm saying plan for the worst, hope for the best.

2) Have a talk to baby and tell him/her they need to come 6 December, because that's the best date to be born on anyway Like the point above, feel the fear and do it anyway. Plan for the worst and hope for the best. Work it through so that you don't feel this issue affects your labour or your ability to bond with baby. It's completely understandable to have an aversion to that date, but as you can't control for it, process it so you can come to some peace with it. Either baby will come on another day, or s/he will rewrite what that date means to you.

I understand these things are playing on your mind. Can you try to find the a way to the positive instead of being stuck on the negative? You're preparing to welcome a new bundle. That's a wonderful miracle all in itself. I hope the joy of that can outweigh the sadness of the other circumstances.