The King Onjo of Baekje reference article from the English Wikipedia on 24-Apr-2004
(provided by Fixed Reference: snapshots of Wikipedia from wikipedia.org)

King Onjo of Baekje

King Onjo (온조왕/溫祚王, r. 18 BC - 28) is the legendary founder and the first king of Baekje. He is known as the third son of King Dongmyeong, the founder of Goguryeo. King Dongmyeong had three sons; Yuri, Biryu and Onjo. As Yuri, born from King Dongmyeong's first wife in Buyeo, came to Goguryeo and became the heir of throne, Biryu and Onjo left Goguryeo and moved south to found their own kingdoms.

Biryu (비류/沸流) founded his in Michuhol (미추홀/彌鄒忽), but his didn't last long. The modern-day location of Michuhol is in debate - it was known as Incheon for a long time but recently it was suggested as Incheon County, City of Asan, South Chungcheong. Onjo found his kingdom in Wirye, modern-day Seoul and named it Sipje (십제/十濟). Biryu's people joined Sipje after Biryu's death and King Onjo renamed it to Baekje.

Whether the legend tells the truth or not, it indicates that Buyeo, Jolbon Buyeo (aka Goguryeo) and South Buyeo (aka Baekje) shared a common origin.

Preceeded by:
None
Kings of Baekje Succeeded by:
King Daru