[Jonathan D]

There were some 1st-cousin marriages in my lineage way back but they're far from the most confusing relationship.
My g-g-grandmother Amanda married her first husband, George (a widower with 10 children) when she was 22 and he was about 65. They had 4 children, the oldest being Becky. When Geo. died she married a man her own age and had 4 more, the oldest being Henry.
Emily, George's granddaughter by his first wife, married J.L. and had a daughter, Kitty. When Em. died JL married Becky, Em's [half-]aunt, though she was 10 years younger. George and Em's daughter Kitty married Amanda and her 2nd husband's son Henry and had my grandfather.
These marriages made Amanda my grandfather's grandmother, [step] g. grandmother, [step] g.g. grandmother], and Becky his [half] aunt, [step]grandmother, and [half]g.g. aunt. Her kids were his aunts/uncles and first cousins.

Any strange relationships that don't involve actual inbreeding in your line? I'd love to hear about them.
Above should read "Kitty married Henry, who was the son of Amanda and her second husband". "Kitty married Amanda" may sound odd or at least like she was a bit ahead of her time.

Amanda was (my grandfather) Mustang's grandmother biologically (mother of his father).
She was his step-great-grandmother because she was the mother of his step-grandmother, Becky.
She was his step-great-great-grandmother because she was the widow of his great-great-grandfather, George.
Becky was his step-grandmother because she married his grandfather.
She was his [half]aunt because she and his father had the same mother (Amanda).
She was his [half]great-great-aunt because her father was his great-great-grandfather.
Her 11 children were uncles and aunts of Mustang (and his 15 siblings) because they were his mother's half siblings. They were his cousins because they were his [half]aunt's children.
Mustang's mother, Kitty, and her father, JLR, had the same mother-in-law (Amanda).