In our family there's birthday books .... very different from the Family Bible (also have this too)...
The earliest one in our family was owned by a lass born on the Victorian Gold Fields (Australia). In her handwriting she recorded her name against her birthdate, when she was around 8 years of age, and in that same childish handwriting she wrote her older and younger siblings on their days, and their parents, and the uncles and aunts, and neighbours and school friends too.
When each of her parents died, she wrote those dates in against them also. As an adult, she added the birthdates for each of her inlaws (including their parents too), and so on. When someone married, she noted the date of their marriage and to whom ....
When she died her birthday book was already in the hands of her favourite niece who was her namesake. So the tradition continued, and there became a need to obtain a new birthday book. The new one has all the rellies, in their own hand, and of course, there's so much information that can fit on each line (books are hand held, so quite small) and there's now additional books.
The earliest book has been digitially photographed, and the second one is being done later this week. Yes, there's some names that wthe current generation does not recognise YET but .... this will sort "in due course"...
And, yes, between several of my generation, we have bought up a number of "new" birthday books, in anticipation that these will be as scarse as hen's teeth and we are anticipating these will be for the future Grans in our family to hand on as gifts to their own grandchildren...
So, the birthday book's eldest person mentioned would be two of my great great great grandparents born 1805 and 1809 ..... And, yes, my cousins and I do spend pennies on confirming BDM certs

Cheers, JM