OP, if you’re the poster I think you are - your late partner was quite severely abusive and his parents are overbearing and controlling.
Please, please do NOT let the opinion of these people affect your decision to have a baby with your new partner. It is quite literally none of their business who you have a relationship with. It is bad enough that you’ve been made to feel you’ve had to keep your new relationship secret - it would be a total bloody tragedy if you terminated a pregnancy you wanted to go through with just because your other kids’ grandparents didn’t approve. Seriously.
Why are you letting them control you like this? To be horribly blunt: their son is dead, and you are entirely at liberty to have a relationship with anyone you wish. It’s irrelevant that he was a friend of your late partner. There is no betrayal here, because your late partner is no longer alive to be betrayed. That might sound harsh, but it’s entirely true.
If you are who I think you are, your late partner’s parents are not good people and are intrusive and weird and seem to think they have some kind of say in the decisions you make for your children. Here’s the thing: they don’t. If a parent dies, the grandparents do not get to step into his place and act as if they have the same rights he would have done if he were still alive. That just is not how this works. You really, REALLY need to start putting some boundaries in place with them and frankly, if they step back as a result, that will be a good thing.
Nobody - nobody at all - should have a termination for any other reason other than that she wants one. If you don’t want a termination, do not have one - least of all because two people who happen to be your kids’ grandparents might be pissed off. They’re awful, awful people if they are.