According to the history compilation Samguk sagi, he was the son of the previous king Gaeru.
[1] Relations between Baekje and the rival kingdom Silla became hostile after Gaeru had given refuge to a Sillan traitor Gilseon in 165, shortly before Chogo inherited the throne.
[2] Chogo began attacking Silla in 167, and captured two castles, but the Sillans drove him and his army off.
Samguk sagi: The 8th king Goi is said to be Chogo's younger brother.
The 13th king Geunchogo apparently took Chogo's name to emphasize his lineage after a long rivalry between two royal factions.