"Did Catholics write their genealogies on the insides of their family bibles?"
I have personally wondered this, and posed this same question to many different people both in the United States and abroad.
It seems that the answer is, "Not traditionally, no. This is more of a Protestant tradition."
But there are exceptions. On a visit to NCSML I was allowed to look at the stacks in the back of the library, and I found a Czech prayer book with a written genealogy in it.
Perhaps we can discover whose it is?
Or perhaps you have more insight into this issue?