My mom and I were having a conversation about how soon my elusive father is coming to visit. She fusses about him but they get along in the end.
"Maybe it will be nice to be together", she said finally. "After all, we're both his blood grandparents." (I think she said "blood" to differentiate from the steps.)
I pointed out that no, in fact, neither of them are Jo's "blood" grandparents. She was startled, and said, "Oh. I actually forgot."