How can I support my brother who has bad self esteem/confidence?

I’ve got a twin-age brother who’s also my best friend. (He’s a bit older, we’re both males 26M 27M) We grew up side by side, did everything together, sports teams, and we even bought our first house together.

The thing is, he’s struggled with low self-confidence for as long as I can remember. And it’s confusing because nothing on the surface points to why. He’s smart, good-looking, naturally talented, great at sports, and has strong social awareness. People genuinely like him.

But despite all that, he can’t shake this insecurity. He won’t approach girls even when he wants to. He avoids making decisions without checking with someone first, whether it’s outfits, plans, or anything else. He needs validation on almost every choice.

His work has a casual day once a week, but instead of wearing something he likes, he sticks to the company shirt because he’s scared of standing out or looking weird. And he actually has friends there, so it’s not like he’s socially isolated.

I really want to help him build confidence, but I’m not sure what the best approach is.

For anyone who struggled with low self-esteem in the past: What actually helped you get out of it? And for those who supported someone through it, what made a real difference?

I’d love advice on how I can be there for him without overstepping.

I also want to note that out of all the things that we do together, 8 times out of 10, he is significantly better than me at. So it’s not a matter of comparison in terms of sports or book smarts, because he is clearly better than me at both of those things.

Edit:

I will say I think he does compare himself to me when it comes to the dating world because I tend to have a bit more luck with the ladies. He’s only been in one relationship. And I think this is where some of his issues stem from because he did have a horrible abusive girlfriend that he stayed with for over a year and a half.

Thanks all