Game concept
Noble Family
The game also links it as Noble Families, Noble Family's.
From the game's encyclopedia
Noble Families are powerful Houses in a Bureaucratic Realm. They own an Estate, controlled and managed by the House Head, and remain an integral part of the Realm at all times, as they will attempt to gather Influence and secure Provinces for themselves.
An influential Noble Family may become a Powerful Family or a Dominant Family.
The game's text for patch 1.20.1.2. Words in blue are entries of the encyclopedia: hover one to read it, as in the game.
Noble Family is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "Noble Families are powerful Houses in a Bureaucratic Realm." It is part of Administrative. It covers Powerful Family, Dominant Family, Imperial Family and Regent Family. The game also links it as Noble Families and Noble Family's. Patch 1.20.1.2, from game/common/game_concepts/07_ep3_game_concepts.txt and game/localization/english/game_concepts_l_english.yml.
Source: game/common/game_concepts/07_ep3_game_concepts.txt, game/localization/english/game_concepts_l_english.yml and the English localisation, Crusader Kings III 1.20.1.2.