Game concept
House Head
The game also links it as House Heads, Head, Heads, House Head's.
From the game's encyclopedia
Every House within a Dynasty has a House Head, who wields certain unique powers over the members of the House.
Notably, the House Head can legitimize Bastards, call the members of the House to War and demand conversion of Landed members. The House Head also gets a Weak Hook on all members of their House that are born while they are in power.
When they die, their Primary Heir becomes the new House Head.
Clan House Heads have special rules and privileges.
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.
House Head is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "Every House within a Dynasty has a House Head, who wields certain unique powers over the members of the House." It covers Clan House Head and House Head Interaction. The game also links it as House Heads, Head, Heads and House Head's. Patch 1.20.1.2, from game/common/game_concepts/00_game_concepts.txt and game/localization/english/game_concepts_l_english.yml.
Source: game/common/game_concepts/00_game_concepts.txt, game/localization/english/game_concepts_l_english.yml and the English localisation, Crusader Kings III 1.20.1.2.