Re: Prepping siblings
My kids are older as this was an oops baby. My boys are 13, 11, and 7.
One thing I have spent a lot of time doing, even before I was pregnant, was talking a lot about behaviors of mammals, and how mammal babies are all basically the same in what they need. My kids have always been very science-minded and innately good with animals, and I know this will transfer over to being big brothers.
I have also stressed that babies cannot communicate with words, to say, "Hey, I'm hungry/lonely/sad/tired," and so to get what they need they cry. Crying is supposed to elicit help -- you aren't supposed to like the way it sounds, it is purposely bothersome. I know a lot of litle children get very disturbed when babies cry, so this is a point I stress to my kids even though they are not so little.
I take the opportunity, when we are out and about and we see/hear babies crying, to talk to my kids about what might be wrong with that unhappy baby. Mostly we chalk thig up to, babies aren't made to be happy alone, in their crib/carseat/whatever. They are not programmed to thrive that way. Think about where the baby is now, all warm, squished, secure -- he never gets hungry, he never gets cold, bright lights aren't an issue, flailing limbs don't happen. Then he's born, and wow, I'm cold, it's bright, I cant' control my body, what's that happening in my stomach? And where's that lady??? How can I get back to that lady? So we talk about how "needy" newborns are designed to be, so they don't get picked off out in the wild, lol.
I will admit it is easier to prepare older kids, but the advantgae to younger kids is, often they don't have much of a memory before the baby, so things can settle back into normalcy faster.