Game concept
Initial Legitimacy
From the game's encyclopedia
The Legitimacy a Character has when they become landed.
It is calculated based on Level of Splendor, relation to their predecessor, Court Grandeur, gender, Bastardy, years as a Ruler, the Legitimacy Dynasty Legacy, Diplomacy, Virtues, Sins and other special Traits, like Sayyid, Diplomat and Just.
Heirs will inherit 25% of the previous ruler's Legitimacy if inheriting a higher Tier Title.
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.
Initial Legitimacy is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "The Legitimacy a Character has when they become landed." It is part of Legitimacy. Patch 1.20.1.2, from game/common/game_concepts/06_ce1_game_concepts.txt and game/localization/english/game_concepts_l_english.yml.
Source: game/common/game_concepts/06_ce1_game_concepts.txt, game/localization/english/game_concepts_l_english.yml and the English localisation, Crusader Kings III 1.20.1.2.