are you misunderstanding? i said one of the adopted white Wong children marries another white person and they have a white child with the surname Wong...
If the two adopted kids in question are female then their surname would change from Wong, And even if they didn't want to get married the child would most likely take on the father's last name
regardless, a white male adopted Wong having a child with a white woman would result in another white Wong. so it isn't completely impossible... there's always gray area.