Game concept
Powerful Family Rating
The game also links it as Rating, Family Rating.
From the game's encyclopedia
Powerful Family Rating is a measure of how influential a Powerful Family is.
While there are many ways to increase a Family's Rating, the main factor is the number of held Governorships.
A House must have a Rating of at least 40 to be considered Powerful.
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.
Powerful Family Rating is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "Powerful Family Rating is a measure of how influential a Powerful Family is." It is part of Powerful Family. The game also links it as Rating and Family Rating. 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.