Lan Wangji and Lan Xichen
Wangji wasn't going to try to change the seating in anyway as soon as he saw the happy look on his face about just having a simple conversation with his brother. He figured one of them would sit next to one of the brothers and then continue with any conversation that they decided to have.
There was the whole conversation of what they planned to do for their partners on the actual day of Valentine's Day since that was meant to be the special day.
"If he knows anything about these he has not shared with me. But he was busy trying to adjust to all of the cultural difference when he arrived here."