They have been dancing around something for a while, the three of them. Sizhui knows other grown children do not have this kind of closeness with their parents. This kind of heat. Of course Hanguang-jun isn’t his real father, nor is Wei Wuxian. But the two of them are the closest he has, and his love for them is hopelessly twined with whatever this is.
This is warm and lovely and made me smile, the inclusion of Sizhui feeling strangely not-wrong at all.