Two of the most popular posts have been Naked Brothers Bonding
and Boner Brothers.
It makes sense, then, I'd get an email asking if it's "normal" for brothers who are in their mid-thirties to still get together on a regular basis for some mutual masturbation.
Define "normal." It's very common for brothers - especially if they share a room - to jack off together.
It's even more likely with twins or triplets.
As you grew up, you found it pleasurable, right? So, why wouldn't it be pleasurable now?
What changed other than your age?
If you and your brother enjoy it, go for it. There's nothing stopping you.