Cousin Abe?

At the Lincoln Memorial- 
I've learned a few things in the short time that I've been researching my ancestry. One of the most important is that one needs to locate specific records. This would include census documents, newspaper articles, and birth, death and marriage records.
I've perused the various ancestry message boards looking for clues of my own ancestry, and sometimes found valuable information. Before adding any of this newfound information, I like to double-check the data. I've seen hundreds of family tree errors, due to people outright copying unchecked information from others.
My mother used to tell us we were descended from William the Conqueror through our Shipley family, and I've seen that indicated on several sites. As I've not yet found the true father of Adam Shipley (supposedly the first of our family to arrive in America,) I cannot claim this as true.
Then there is the enigma of Abraham Lincoln's heritage.
I did some extra research yesterday, and found the two common beliefs about his family were about equally divided.
The side I'd like to believe states that Abraham was the son of Nancy Hanks, who was the daughter of Lucy Shipley. Lucy was the daughter of Robert Shipley Jr., who was the son of Robert Shipley. Robert Sr. was one of Adam Shipley's six children.
I'm descended from Robert Sr. as well, and also from Robert's brother Peter, so of course this story appeals to me.
The other side believes Abraham was the illegitimate son of Nancy Hanks, and that her mother may have been named Lucy, but not Shipley.
Apparently Abraham Lincoln's body is now encased within tons of concrete, and not available for DNA testing, so we may never know the truth about his birth.
I guess there are some things only a mother knows for sure.