Well, Orange, I want to express to you how much I feel for you.
AS you said, you signed papers for adopting the children in case of... Usually, someone signs those papers without imagining something could really happen. Unfortunately, it did.
There will of course be some difficult times with the kids : their parents are gone, it will be tough on them, and when they'll be teenagers, you may hear stuff like " shut up, you're not my mother ". But in the end, these kids love you for what you've already done, and for what you will do.
Of course, I think it won't be very easy with giving birth soon, but now you should focus on your family and enjoy life as much as possible. That's a humbling lesson.
I am not mentioning the following to give you a lecture, but just to prove that I understand ( I am 24, besides ):
My grandsparents ( dad's parents, sole child ) committed suicide in May. It was a shock for me (and my dad of course). After that, there were difficult times, but now I've learned that some things do matter, and others do not.
I used to yell at my husband for some things he would do ( or not do... ). Now I don't. I'm like: that's not what matters.
Feel free to send me private messages if you'd like more personal support.
Best wishes for a brighter future to you and your husband.