肉親
にくしん · nikushin · JLPT N1 · noun
kinship
🩸 肉 flesh + 親 kin: relatives who share your flesh and blood, not through marriage
肉 (flesh) and 親 (parent or close kin) combine into 'flesh-kin', meaning relatives bound by shared blood. 親戚 can also include in-laws, but 肉親 cannot.
肉 — pictograph of a slab of meat with ribs/striations
肉 is a pictograph originally depicting a piece of butchered meat, showing the outer cut and the striations of muscle or ribs inside. The character has meant 'flesh' or 'meat' since oracle bone times. As a radical it is usually written 月 on the left or bottom of characters relating to the body (e.g. 肝, 胃).