Honestly, this feels as impressive as getting the correct answer to "Hey Siri, what's the weather like tomorrow?"...

I too would do it manually and begin by trawling through emails from my brother's address. Obviously just the word "Monty" means the brother probably mentioned the name somewhere else (e.g. in real life) and then just used that reference key assuming OP knows what/whom it is referred to.

It's somewhat impressive that an AI can infer that "this email's subject is a male name, and the email discusses his reading preferences, it's possible the email sender is talking about his son." (I wonder if AI would "understand" (whatever "understanding" means for AIs) that the email sender is not talking about a cat named Monty, because cats can't read).