Maybe it was just a typo or an oversight, but to which side of the family does "Grampa" belong? He and grandma seem to be the parents of Lily's mother, which would make Feldspar her maiden name. But then why would Lily's last name be Feldspar? (Unless this is the rare case of a person marrying someone else with the same surname.) There doesn't seem to be a divorce or anything like that in their past is there?
I could dither about Mr. Feldspar placating the old bats by taking their family name as his own..... but truth is I blundered that one.
It's a working explanation, though, so let's go with it.
"What was that popping noise ?"
"A paradigm shifting without a clutch."
--Dilbert