My husband can trace his American ancestry back to John Maxfield of Maine. Maxfield was one of the first Europeans to go to Maine and not run away. He can also trace back to a different (probably father) John Maxfield in England. Then it goes a bit further back. Which all makes sense and is traceable via tax, church, legal records. It gets weird when it starts being traced back to Normans, Welsh, Vikings (Norse), and a Roman in about 350 AD. How do the people who trace these things figure this stuff out? It is all official, so not one of those "buy a family tree" scams.
My poor family is impossible to trace. 1700s on my mother's side and 1850 on my dad's side.
I wrote an answer about this a little while ago, which I like to call "Why having a famous ancestor who lived 1000 years ago does not make you exceptional in any way." To give you the TL;DR though:
Sorry to burst your husband's bubble, but the only interesting part of his early family tree is the fact that he can point to the paper trail (Side note, I would point out that in the Norse branch, he should be hitting the god Odin around 500 CE, so I hope he isn't taking that too seriously). Admittedly, that is a REALLY cool thing to be able to do. I like being able to as well! But the simple fact of the matter is, that if you go back ~1000 years of European ancestry, every single person alive today is related - 40th cousins, give-or-take. So that family tree he has which shows Charlemagne, well, that is your family tree as well, you just don't have the paper work necessary to show exactly how.
hi! it might be worth x-posting this question to /r/Genealogy; that's the family history research specialist sub, so they may have more insights for you