I was pretty anxious about how well Cole would do adjusting to life with a baby brother. His life as he knew it was about to be turned upside down - and sharing his Mama's attention has never been one of his strong suits.
So I tried to slowly prepare Cole early on for some of the upcoming changes. Chris started taking over some of "my" usual duties with Cole - bathtime, bedtime routines, etc. I talked to him a lot about how I wouldn't be able to spend quite as much time with him as usual (not a huge transition, since Cole usually plays independently anyway). We also made a conscious effort to teach Cole how to independently do a lot of the things he often asked us to do: change his clothes, wipe his bum, brush his teeth, get a snack. All of these things together helped make the transition easier on the both of us.
Lastly, I made sure that Cole did (and still does) know that it's ok to not be fully happy about being a big brother. It's a huge change, one that he had absolutely no say in, and I think it's vitally important for kids to know that they are allowed to feel all their complex feelings and still know that we love them, no matter what. I'm always upfront with him about Chase - "Sometimes it's really frustrating to listen to him cry really loud like that, isn't it? I wish he would feel better too." "Having Chase was a really big change, wasn't it? How do you feel about it?"
Fortunately, so far the transition has been far easier than I anticipated. I try hard to give Cole plenty of attention when it's feasible (lots of reading books while I'm nursing Chase) to fill up his attention-tank to make up for the times I'm needing to tend to Chase. Plus, it's been hugely helpful having Chris around to give him tons of one on one time.
Cole simply adores his baby brother, asking to hold him constantly and always, ALWAYS willing to stop whatever he's doing to give him his bink, or change his diaper, or cover him with a blanket.
I'm hopeful that this means they will have a life-long friendship with each other.