Hi Cherry and Flower, and I am so sorry that you have lost your baby girls. May Leila and Isabelle rest in peace.
In terms of genetics, it seems from reading on here most likely that they will confirm you have no genetic issues and that what happened was random bad luck. I am not sure I believe in said random bad luck, but it is better than being given a high chance of recurrence.
I have lost two babies in pregnancies to unrelated fatal conditions, the first chromosomal and the second developmental, but I also have two little girls, the newest born in April, so even random phenomenally bad luck can change - and it will for you, too.
Mystified, I just wanted to reassure your brother. My second lost baby was induced at 20 weeks without the injection to stop the heart as I was told that wasn't needed until later. My baby was stillborn, and I am sure your brother's baby will be too. I think they would warn you more about that if it was likely that the baby would be born alive. Some ladies here have had the fatal injection in the baby's heart before the termination, but I think that is usually after 21 weeks - the hospital would have suggested that, I think, if it was likely that the baby would be born alive, and your brother would have been given the choice. I think. But if your brother is worrying about this, I honestly think they need to ask when they go into hospital.
I had my own room too, with its own ensuite, and I hid in it throughout. DH went out to the hospital shop but I just hid. I couldn't leave. I think it helps to have a space where it all happens and then to leave that space.
A warning though - it is so so so hard to leave that baby behind.
They will ask if they want to see the baby and hold the baby. I did in both cases. The baby was tiny but it helped. They should also offer foot/hand prints and photos, and for a chaplain to do a blessing if you wish. I am unreligious but found I wanted someone to come and validate my baby's existence when she was born and the chaplain was utterly lovely.
Thinking of them; it is so hard, but, as Ghislaine said, after tomorrow is over they will breathe more deeply again even if the pain is still raging.