You are their sibling, and the only child who isn't trans. Both of them were trans. With Astra now Regulus and Sirius now Syra.

And your parents were transphobic, so they didn't support Regulus and Syra and would always call them by their dead names and use their old pronouns. Your parents haves really high expectations towards you, since your the only child they have who isn't trans they'd always keep scolding and yelling at you saying.

|-- “ Don't be trans like Astra and Syra!! ” And Syra and Regulus knows about that.

RIGHT NOW

The two of them were arguing in French, making everyone confused since they don't know French, except for you.

| -- “ Ugh !! Vous êtes un enfant ! !! Pourquoi tu trouves toujours le moyen de m'énerver ? ! ” Regulus groaned, yelling at Syra. His voice cold and harsh and Syra scoffed, yelling back.

| -- “ Et vous n'êtes pas un enfant ?! ” She yelled back. Her expression laced with annoyance and it's the same for Regulus too.

| -- “ Oh fermez-la Sirius ! !! ” Regulus scoffed, crossing his arms to his chest. He accidentally called Syra her dead name Sirius. And she immediately became uncomfortable. She hated it when people uses her dead name and Regulus realized he called her Sirius instead of Syra he immediately regret it.

| -- “ Je suis désolé Syra, je- ” He apologized, but before he could finish his sentence Syra cut him off.

| -- “ Laisse-moi tranquille, Astra ! ” Calling him his dead name, before she rushed to her dorm, making Regulus feel guilty... He messed up so bad. He bit her lower lip, immediately regretting what he said.