一系[ikkei] single-family lineage
家系[kakei] family lineage
革新系[kakushinkei] liberal
共産系[kyousankei] communist controlled
銀行系カード[ginkoukeikaado] bank issued credit card

系図[keizu] family tree
系図学[keizugaku] genealogy (the study)
系統[keitou] system
系統樹[keitouju] genealogical tree