It’s a little confusing. He travels back ten years to become friends with his brother? The question “why aren’t they friends”? jumps me out of the story. Don’t make the reader ask questions you don’t answer.

I got the impression (this is when readers make bad assumptions) that perhaps 10 year younger brother doesn’t recognise him. I don’t think 10 years is enough to pull off that trick. I may be completely wrong, but your logline isn’t selling me on it.

Perhaps how he dies would stop me asking or thinking the wrong things. It would also hint towards genre. Is he murdered, dies in a car crash etc…

Perhaps rather than become friends. You phrase it in a way that describes brotherly love. I have great friends, but they are not my brother.

Also it is tradition not to use names unless it is part of the story, as in Billy the Kid. A name has different meaning to different people, even across cultures. There are names in Australia that have no meaning whatsoever outside my country and names from other countries that bring a childish grin to an Australian.

I like time travel bits. I hope this has helped.