I have a wallet.aes.json file backup from blockchain.info (from 2013), I know first password, but I forgot second, I know about which might be but I do not know the exact variation, 12 phrase word is lost too.
If you know how it should look like, but just don't know the exact variation, bruteforcing should be doable in a reasonable amount of time.
What exactly are you missing in your variation ?
Do you know the amount of character ? Are you just missing a few one ?
Is it about upper / lower case letters ? Are you looking for a permutation of your characters ?