I'm more just thinking with the whole "adventurer" thing. Yes they are technically part of the family, but no nobles, and no chronicler would ever record them as being such.
There would also be many more family members than ever listed on the family page.
Now, yes, families were obsessed with their own lineage, but it wouldn't be something freely accessible for every single person who just wants to check. The records would be hidden probably on the family estate and no one would never have a copy of it.
