Books for brothers?

Hello!  First time posting, and I’m hoping I can get some good suggestions.

Looking for good read-aloud chapter books about siblings, specifically brothers.  I have three sons, two of which are ages 6.5 and 3.5.   They share a room and are each other’s world … except that they fight, scream, work AGAINST each other constantly.  My older son does not look out for his younger brother, picks at him, just makes things more difficult for my younger son.  It’s strange, because in every other aspect of life, he’s such a sweet, nurturing child.  It’s a recent development, which I can see rooted in jealousy of his younger brother, and my husband and I are taking measures to undo this habit of being disrespectful in this way.  My younger son is becoming more aggressive and retaliates in a number of ways.  The most common thing is to squeal/cry/fuss at the top of his lungs for much longer than necessary.

They both connect to literature and I’m hoping to find a good chapter book that exemplifies brotherhood, bravery, taking care of each other and working together for the greater good to read to them.  I want them to understand that they have such a precious gift in their brotherhood.   I get it that kids fight a lot, but along with the other measures we’re taking to quell this ugly period, I’d love to help it click with a few good stories.