I know I'm late on this- but your story sounds very similar to mine! I have brother and sister siblings, but brought them home at different times.
Lockjaw was first and he came home at 7 weeks. Same thing- when I saw his sister became available, I jumped at the opportunity. Penny came home 5 weeks later at 12 weeks.
Much of their behavior mirrors how mine were. It took a few months, but at almost 1 year, they LOVE one another! Still have their little spats here and there, but you can really see their bond.