The kohen gadol is responsible to pray for the welfare of the nation: Makkot 11a
The kohen gadol's family
Whether a substitute wife was set up for the kohen gadol to marry on Yom Kippur, if his wife would die, so that he could serve as a married man: Succah 24a
Under the rule forbidding the kohen gadol's marriage to a woman who isn't a virgin, "virgin" refers to a woman who has never had sexual intercourse: Niddah 8b
The mother of the kohen gadol would provide food and garb for accidental murderers, to keep them from praying for the kohen gadol to die: Makkot 11a
What would happen if a kohen gadol attempted to marry a widow: Temurah 5b