姻戚[inseki] relative by marriage
遠戚[enseki] distant relative
外戚[gaiseki] maternal relative
休戚[kyuuseki] weal and woe
親戚[shinseki] relative

親戚知己[shinsekichiki] relatives and acquaintances
憂戚[yuuseki] grief
縁戚[enseki] relative
親戚関係[shinsekikankei] relations
親戚眷属[shinsekikenzoku] one's family and relatives

其れ故に[soreyueni] and so ...
何故なら[nazenara] because
何故ならば[nazenaraba] because
エンジン故障[enjinkoshou] engine failure
縁故[enko] relation

何故かと言うと[nazekatoiuto] because
旧故[kyuuko] antiquity
故い[furui] old (not person)
故老[korou] old people

懐旧[kaikyuu] recalling the old days
旧ソ連[kyuusoren] former Soviet Union
旧悪[kyuuaku] past misdeeds
旧衣[kyuui] worn-out clothes
旧詠[kyuuei] ancient poems

旧怨[kyuuen] old grudge
旧縁[kyuuen] old relationship
旧恩[kyuuon] old favors
旧仮名遣[kyuukanazukai] former (i.e. before the post-WWII reforms) kana usage in writing the readings of kanji

育ての親[sodatenooya] foster parents
育て親[sodateoya] foster parent
１等親[ittoushin] first-degree relative
仮親[karioya] adopted parents
近親[kinshin] near relative

近親婚[kinshinkon] consanguineous marriage
近親相姦[kinshinsoukan] incest
懇親[konshin] friendship
懇親会[konshinkai] friendly reunion
似非親[eseoya] distant disinterested parent