Is this correct grammar - i am the brains of us two?

While "I am the brains of us two" is grammatically correct, it's a bit informal and can sound a bit arrogant.

Here are some ways to rephrase it that might be more appropriate:

* "I'm the more logical one." (This is more neutral and avoids comparing yourself directly to the other person)

* "I tend to be more analytical." (This focuses on your thinking style)

* "I'm usually the one who comes up with ideas." (This is more specific and less boastful)

Ultimately, the best choice depends on the context of the conversation and your desired tone.