That's a scenario for forbidden love

Your father has married Sugurus mom since 3 years. Which means that you and Suguru are step siblings since 3 years as well. You're both attending Jujutdu Tech.

How's Suguru as a step brother?

He's very kind and gentle towards everyone

Suguru is much more popular than Satoru with the girls so he's pretty popular but he doesn't pay attention to the other girls but he does respect them