My mother's name was Wood. But growing up, we always referred to her family in the plural, because there are so many of them, aunts, uncles, cousins, etc. But over time, this got me confused and I never actually knew what their family name really was -- until I started searching records.
Turns out, even in official documents, no one else knows either.
My mother and uncle are twins, born minutes apart -- the same doctor, same staff. On their birth certificates, one is named Wood, the other Woods -- including their father on each, one Wood, the other Woods. The same doctor delivered all the older children, all named Wood.
All the rest of the family go by the singular, including ancestors.
Another set of ancestors are Necessary, but at some point, one branch of the family changed their name to just Essary. The story is that the patriarch originally changed his name to Necessary from ? because he was running from someone/something.
Official records are only "official" because they were recorded by governmental officials. But they often made mistakes and typos, and if the families couldn't read or write, then it was left up to the officials in charge to determine the "correct spelling", and they only know what they are being told.
Long story short... you may need to compare with the other family members, and then make your best guess (but document your reasons).
