An Overgrown Family Tree

(My twin sisters and I are at home. I have often been mistaken for a boy and once as my father’s grandson. I overhear my sisters talking and join in.)

Sister #1: “So I could say that my best friend’s brother is my sister.”

Me: “What?”

Sister #1: “I said that my best friend’s brother is my sister. [Sister #2] is my best friend and you’re her brother, but you’re my sister.”

Me: “Right. And I also happen to be your father’s grandson.”

Sister #2: “Exactly. So my father’s grandson is my sister, who is also my best friend’s brother.”

Me: “Or your father’s grandson, who also happens to be your best friend’s brother, is actually your sister.”

Sister #2: “Seems legit.”