The Nineteenth, it is possible that you are of royal descent.
One of my lines leads back to Royalty - a royal female who married one of my ancestors, so their children were not royal - and there are other lines who came over with William the Conqueror but were not related to him. The reason I know this is because prior to 1837, the families lived in small villages and the parish records are very good with lots of info re BMDs, also I've visited the villages and the churches and looked at the parish records. As I researched further back, I found my ancestors were married to knights, or sons of knights and at this point, you only have to look in Burke's Peerage to follow the lines back through the centuries.
This was the tree of my g.grandmother - pity her family was so poor that her father and 2 brothers lived in the workhouse at one point (the girls in the family stayed home with mum) and her grandfather (my 3 x g.grandfather went to live in the workhouse when his daughters died and his son in laws didn't want him any more. He died in the workhouse). This was down to generations of being descended from the first son of the first son, only then to become descended from one of the younger sons who wasn't bequeathed a manor house and/or money and titles.
Only a couple of generations previously the family were merchants, then a few more generations back to mid 1500s, they were Lords of the Manor and so on back to the Knights, one who died on the way back from the Crusades, and eventually back to a someone who accompanied William the Conqueror in 1066, who appears to have been a butler but was knighted and given the title of Lord when William the Conqueror was crowned at Westminster. Interestingly the royal lady who married into my family married again - I assume somehow she got divorced, because she and her first husband died within a couple of years of each other in their 60s, but she had a daughter with her 2nd husband and two of her grandchildren, offspring of children of both her marriages, ended up marrying each other, my family tree calculator suggests they were half first cousins.