Discovering Consanguinamory in the Family Tree

I am [or, had been] active on [a certain Big Online Portal's question and answer service], especially when it comes to explaining the importance of relationship rights, full marriage equality, and decriminalizing consanguinamory. Someone had this question...

Family Tree Concerns..?
My Grandfather recently passed away and my Grandmother told us all that her and my Grandfather were never married, they had always celebrated an anniversary (or so we thought,) but didn't understand while she waited till he died before telling us. After further research into my family tree I have discovered that my Grandmother married her Uncle (is this incest!?!), my Mother feels all weird because it feels like her life has been a lie and the only person she could have asked and got a proper answer was her Dad but now he's gone so we are both just looking for some advice or if anyone has been or is going through a similar situation...

This was my answer, which was chosen as the best answer (thankyouverymuch)...
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Here's what matters: Was your grandfather a good person? A good spouse to your Grandmother? A good parent? A good grandparent? THAT is what matters, not any genetic or legal relation to your grandmother. There's no lie about any of that. Your mother's life is no different now than it was before she knew that information. She's just allowing cultural prejudices to influence her reaction. Your grandparents had what is called a common-law marriage. As long as they were good to each other, that is what matters.

You didn't make it clear, but it appears you mean your grandfather was the brother of one of your grandmother's parents (he would still be an "uncle" to her if he had, at one time, been married to one of your grandmother's parents' sister without any biological relation to your grandmother). Assuming there was a genetic connection (though it is possible he had been adopted into the family, too), that is still no reason for alarm. This is much more common than people think. People are finding out about this through DNA testing and family records, although family records don't always reveal the truth.

You don't have to go too far back in anyone's family tree to find these kinds of things. I doubt there is a person out there whose ancestry has nothing like this.

In other words.... you and your family are as normal as everyone else.
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Just about everyone has incestuous childbearing in their family tree. In some cases, someone was raped, which  of course is a horrible,  or there was cheating. In other cases, it was true love between people who were not cheating on anyone. If the law prevented them from legally marrying or from telling the truth, that is a problem, a terrible problem, of the law, and just one of many reasons we need full marriage equality. It is not something wrong with the lovers.