Yes, there was a period of upheaval, confusion, dc1 torn between pleasure in the new sibling and jealousy. But then a good deal of joy in seeing the pleasure they got from one another. And finally, a reassurance, seeing that they are able, as adults, to talk to each other and confide in each other at times when, for one reason or another, they can't confide in me. And the knowledge that that support will be there long after I am gone.
I was also a younger child in a family with 4 children. And yes, of course my elder brother got more toys and attention. But I'm 55 now: I don't really need those toys. What I do need is another adult who shares my memories, knows the same jokes, won't accidentally get lost on the way as friends can so easily do, and will be there for me one day when I stand in my parents' empty house. And I've got 3 of those.
I think you can make an enormous difference in the early days of sibling-hood, by being patient with your elder child- but also by accepting that the jealousy is there and, like chicken-pox, it's just another part of parenting that you may have to sit out. You can't make chicken-pox go away by being the Perfect Parent, but it usually clears up in its own time without too many complications.