You don't need to get married to have sex or father a child ....it's all just natures way of ensuring a species evolves and that its unstoppable... It would be good though to have tests to discover if you are closely related....
My grandpa married a cousin. Not first, but I don't know how far they were separated. His family came over a generation before hers ... but her parents died, and his took her in and raised her. They had the same last name even before they married. LOL
I have been aware of a few first cousins that have married. I'd find it strange not knowing who your first cousins were. Anyway my surviving first cousins are all spoken for, unless my uncle who died in Oz 65 years ago had secret offspring.
At one time the automobile was considered a rich man's toy, so nobody saw any reason to build roads for them at public expense. Then industrialists lobbied governments to do just that, so they could have a mobile work force able to travel to where there services were needed. The immediate result was that families were torn apart, as young parents moved around in search of work. Whereas a child formerly grew up among grandparents, cousins and uncles, it eventually became the norm to see the extended family once a year, or not at all.
With teenagers considering the car to be a bedroom on wheels, it was possible that a kid would not even know both parents.
What JakobA said. I know David, Kathleen, Rachel, Alicia, Vincent, Damien, Sarah, Natalie, James, Alison, Alexander, Annette, Kevin, Michelle, Jennifer, Daniel, Rodney, Kathleen (different surname - one is my father's brother's daughter, the other my mother's sister's), Melanie and Joanne very well. Maureen isn't any of them.