What boxers do I buy my brother?

My brother, 23, has a large member and it’s kind of an open secret in our family.

I asked him what he wants for christmas and he just said ‘I dunno, underwear I guess’

What sort of underwear should I buy him?

He’s a skinny guy and doesn’t usually wear boxers that are too showoffy or overstated but I don’t know their brand.

Any help is appreciated?