It's very easy once you get the hang of it, like learning to count back change properly. Siblings have the same parents. When siblings have kids, those kids are each other's first cousins. First cousins have one set of common grandparents. When first cousins have kids, all their kids are second cousins to each other. Second cousins have at least one set of common great-grandparents. When second cousins all have children, those children are third cousins to each other. Third cousins have at least one set of common great-great-grandparents. Earlier I mentioned I had a teacher who was my first cousin twice removed. She was my grandaddy's first cousin, that's all it means. She was his first cousin and I'm two generations removed from my granddaddy, hence first cousin twice removed.
Damn, didn't your momma teach you better. Sharing info like that with a Yankee and a New Yorker to boot. Have you lost your mind!!! Your grandparents are rolling in their graves.
(sings) I'm my own grampa...