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family lineage
「家系」 has another reading with different meanings.
家系を調べるために古い記録を探した。
I searched old records to investigate my family lineage.
この家系には医者が多いと言われている。
It is said that there are many doctors in this family lineage.
家系図を作って親族に配った。
I made a family tree and distributed it to relatives.