You only get presents from one set of grandparents.
They chia'd.
Vader: I felt your presents. Luke: NOOOOOOO
Cancer.
We don't know she hasn't opened her presents yet.
Because he wanted to get a-po-ta-to clock. to make joke more apparent
Because his wife was dead-set against it...
More than one mother-in-law.
Because he fell down a stairs and his dad definitely didn't break his legs.
Your grandparents.
Because they have a common enemy