expression, ichidan verb
be related by blood
Often used in the past tense attributive form 血を分けた (e.g., 血を分けた兄弟) to emphasize a deep, familial bond through shared blood. Can also be used in the negative to deny blood relation.
彼らは血を分けた兄弟のように仲が良い。
They are as close as blood brothers.
血を分けた親子でも
Even blood-related parents and children can have different ways of thinking.