It must have caused an upset at the time - she married a Presbyterian! Dad's grandmother was a Unitarian but the rest of the family was Presbyterian from way back. I know there were some hard words with her preacher brother even when I was old enough to understand, decades after they married. But he was an asshole anyway - told racist evil jokes around young children and used nasty words about African-Americans until the day he died.
That uncle is the reason I began questioning the usefulness of religion in the first place. He was everything I had been taught was evil but he viewed himself as being "godly."
Mom & Dad used to compare religions, translations of the Bible and have long discussions between the two of them about points of religion. While they were politically conservative - especially as they aged - in real life they were always very fair and kind towards everyone.
When the schools were desegregated, my father's brother sent his children to private church schools. Mom insisted that since we would live in a fully integrated country we should go to school with all the people that we would share our lives with. Everyone of those cousins are conservatives (and part of what is wrong with Florida today) while only one of my sisters became a conservative.
On the other hand, my husband was raised in the Unitarian Church and is an agnostic as am I. I claim that if I had to declare a "denomination" it would be the Church of the Apathetic Agnostic, mostly because of their motto, "We don't know and we don't care." http://www.apatheticagnostic.com/
Even as apathetic agnostics, the site has some really nice "meditations" on various subjects, such as Meditation 944 - The Christian War on Christmas. It gives us non-believers some powerful arguments to stand against the whacko religious nuts!