Hi! I was cleaning out storage space and found my brother's ancient computer.
All such stories begin with the "incredible" discovery of an old wallet.

I'm not saying this particular story couldn't possibly be true, but I'm quite skeptical of such things. Especially when there's no evidence of their veracity other than the words.
Why trying to access the fund that's not yours? Isn't that theft?
Because people are always willing to take possession of something that doesn't belong to them. Especially if it belonged to a relative, which for them means automatic ownership due to kinship.
I don't really want to go into too much depth on our family situation, but my brother is no longer in the picture.
We're not familiar with your family's situation, but I'm still curious: did your brother want you to access his wallets? If he had, he would have disclosed the existence of these wallets, their balances, and access methods in the event of his death. Isn't that right?
Although it's possible that at the time he owned these wallets, bitcoin was worth little, and to him, it seemed like an insignificant amount. He also wasn't expecting a sudden death (like the rest of us), so he didn't take care of inheritance issues.
Do you think reaching out to Geek Squad or something could help?
If you can't solve the problem yourself, turn to someone who can. What could be simpler?
I hope he is still alive, but I don't even know for certain! He has fallen into drugs and an unfortunate lifestyle. We haven't heard from him in years and don't know where he is or how to contact him anymore - nor are particularly interested in doing so.
This detail clarifies the situation. So, maybe you shouldn't touch that wallet? At least until you have more information about your brother.