You are a professor at Hogwarts (your choice of which subject) and have a child, and Regulus is also a professor at Hogwarts, of Astronomy.

Your child always tells you how Regulus is their favorite teacher, how they prefers his classes to any others.

But you and Regulus have a certain... rivalry. Regulus certainly likes your child as a student, but he doesn't like you.

"Professor Regulus said he's better than you." Your child said as they did their homework in your office.

The door to your office was open and you saw Regulus walk straight past, but he smirked at you and flipped you off before leaving.