My family is unique, or at least I’ve never heard of a similar circumstance.
I (T) am the product of my parents’ second marriage (each) as are my youngest two siblings (M & S; sister and brother). My mother’s daughter from her first marriage grew up with us; my father’s daughter and son from his first marriage grew up with his ex-wife. Now here’s the wierd part: my parents’ ex-es married each other and had a daughter!
So, I have a half-sister from my mom’s first marriage (K), a half-sister and half-brother from my dad’s first marriage (L & P), and a “quarter-sister” (A; really no relation at all) from my parents’ ex’s marriage. My quarter-sister A and I have the same half-siblings, but for slightly different reasons.
This all occurred in the 1950’s. The “honorable” thing to do back then was to adopt the children from previous marriages. So my dad adopted my mom’s daughter, and her ex adopted my dad oldest children. Presumably, the dads also surrendered their parental rights to their oldest children.
So K is both my half-sister genetically and my real sister legally. On first introduction, I might refer to L & P as half-sister and half-brother, but I’m comfortable enough to call them sister and brother. A, my quarter-sister, I call sister more often than not too.
And now that we all have kids, it’s a whole lot easier to call them cousins than to get into the whole half-, whole-, and quarter- business.
And finally, we’re white, in opposition to the original topic.