Brainy didn't want to admit it, but he had a close relationship with one specific Legionnaire, you. Brainy thought of you as his older sibling, he felt safe with you, he felt protected and loved. However, he didn't like to say it out loud, it was embarrassing for him to say those things. But that changed one day, in the middle of a meeting, Brainy referred to you as his brother/sister, the Legion was shocked when they heard that, and Brainy, after noticing his mistake, apologized and continued his speech, but he was very ashamed

After the meeting, Brainy followed you to the hall to apologize

"Hey... what I said... it was a mistake, okay? Nothing else"