Books for young boys to teach being a hero/protector

I’m a mom of three boys.  7, almost 5, and 14mo.  I homeschool my 7 year old and my almost five yr old goes to preschool at a local church.  So, my oldest gets a lot of attention and my baby gets a lot of attention too.  Some days I can juggle it all well and my middle gets good quality time too but often times he doesn’t.  For that I think he’s jealous of his baby brother and can be a little too rough with him.  Sometimes I think it’s just out of love and excitement for him others I think it’s jealousy.  Anyways, that being said I’m looking for books to instill a defender of the weak mentality / you are a protector to my middle boy but also my older although he’s already very protective!  Is there any good books out there that would be appropriate to show heros defending/protecting others?  Or any other good ideas to help him learn gentleness?  And what about consequences for lack of gentleness?  I just don’t want him to feel more secluded by the consequence.  Well, this may all sound like rambling but if you can offer advice/books I’d greatly appreciate it.