As for why he doesn't call him brother-in-law, it's mainly because it's still too early for that, and calling him "brother" feels more appropriate right now.
Mei Mengchen glanced out of the corner of his eye and saw Pei Ziyu sitting next to her, and noticed that Pei Ziyu seemed to be looking at him as well. He wasn't afraid and started to size him up seriously.
Honestly, judging by looks alone, Mei Mengchen was quite satisfied with him. The circle he hung out with wasn't big, but in his circle, there wasn't anyone better looking than him, so he could barely be considered a match for his sister.
Besides, the two of them had talked on the phone, so they were a bit familiar with each other. Pei Ziyu took the initiative to speak first, "Chenchen, do you still remember me? I'm Brother Pei, the one who often calls you."
"I remember." Mei Mengchen nodded seriously to show he remembered.
