There are two ways to look at it. if you go back to the time of Magna Carta, about 800 years or about 30 generations, you have a billion or more ancestors. That's more than the global population at that time. So there's a good chance that many of your ancestors were knights and royalty. The problem is to prove it, with solid evidence.
On the other hand, there's a lot of garbage floating around, based on no evidence and a lot of wishful thinking.
So, to answer your question: it's possible. But you need good evidence to prove it. Not user-submitted trees on Ancestry.