The third ruler in a dynasty or lineage sharing the same name; for example, King Henry III.
three generations
(literary) Three generations of a family, typically referring to grandfather, father, and son.
three periods of time
In Buddhism, refers to the past, present, and future.
Three Ages
The three stages of historical development in the Gongyang school of 春秋chūnqiū scholarship, later adapted by Kang Youwei to describe different levels of societal peace and chaos.