さんじゅうきょうだいじゃありませんでした
三従兄弟じゃありませんでした
sanjū kyōdaijārimasendeshita

Noun
Desu Copula

The polite, past negative form of みいとこ

1. Was not a third cousin.; Was not a relative by marriage (specifically, a third cousin).

Past/Perfective
Negative
Polite
Terminal Form
Usually Written in Kana