@jimq2
Especially when it was a family that kept family trees covering about 1500 years.
That's bloody impressive, and I'm not sure if you -or the majority of people reading that- realise how impressive that is.
I think the average UK family can only go back to the early 1900's when asked, and would need to do research to delve further back (most people know their grandparents, but not necesarrily their great grandparents). I've managed to get mine pretty much back to 1700, which places me in the top fifteen percent of family genealogists (I'm an amateur, but a stubborn one). Anything beyond 1700, for the most part, requires/relies on personal family records handed down from generation to generation as they precede (UK) state records. Some church records hold more details, but you have to know in advance that your (distant) family members were in that record in the first place in order to ask the church for access permission. A process made harder by the fact that church records no longer reside at their specific churches.
For the most part, any family that has records beyond (before) 1700, were (are) aristocrats.
As an indication of timescale: for Americans the Mayflower was 1620, for the UK, Culloden was 1746. To go back 1500 years puts you in the era when the Romans had lost their sense of humour with the Picts and were leaving the UK and King Arthur, may, or may not have been having extra marital sex with a lake woman...
For reference, when you start delving, the furthest I've managed to get back with documented proof, was my 7th great grandfather born in 1666, in Surrey, England. (you can mostly forget going that far back with Scottish and Irish records), I only focus on direct lineage and ignore the parents and siblings of spouses, and doing so has left me with a family tree of over twenty-five thousand individuals (thank-you COVID for the free time). As an aside, I have found from PM'ng people, that the majority of people with trees over 50K, tend to be either wrong (they just copy other people's trees without actually checking the information and the individuals are correct) or autistic. Mostly it's the latter.