Kingmaker: Game of the 15th Century English Civil War [BOX SET] (Avalon Hill, 1976)
The game is based on the premise that the powerful Noble families used the Lancastrian and Yorkist princes as pawns in a greater game of gaining control of England. Players control factions using their military and political power to control and influence the royal heirs, supporting the heir in their control as king while trying to take down all of the other heirs.
If the game’s setting feels a bit familiar, it should. The War of the Roses inspired George R.R. Martin’s Game of Thrones books and HBO series.