The password was written on paper, he lost it and tried to recover the wallet with a mnemonic phrase
The backup on the computer is disabled.
He could try to recall the word order, but it would still be inaccurate, I guess.
so your brother lost his password that is why he trying to restore the wallet with his seed backup the only problem is it has missing 4 words.
Can you ask your brother if his wallet with password is still there?
It might be much faster to brute-force if he remembers parts of his password than brute-forcing missing words.