Hey Melissa,
Our boys are two and ten months (21 months apart). When we first brought little brother home we would often all crawl into our big bed for snuggles, stories, and prayer time. Often I would nurse our little one while Daddy read the stories. Sometimes big brother would start hitting me or his little brother. We found it helpful to give him words to say instead: “I need Mommy snuggles now please”. This has been huge for us still in helping him to communicate. We also had him practice gentle touches (and still do each time he is overly aggressive).
For us too it has been helpful to let the older hold his little brother and calling him brother instead of baby.
My husband loves to ask our 2 year old, “What’s your name?” Followed by, “What’s your brother’s name?” He loves to shout them both out.
If anything else comes to mind, I will let you know. 😊