I agree it is strange but I’d make one point: It’s possible those passengers with the same last names were indeed the parents but weren’t US citizens even though their children are. For example, I am an American, and my daughter is an American. However, her father is Australian & lives in the US on a Visa. When we travel, his passport is Australian. If my daughter were to be on an international flight with him alone, their last names are the same, but she would be identified as an American and him as an Aussie.
How were those two people allowed to board with stolen/lost passports?
Shouldn’t those passports have been flagged?