Complex sentence: In 37 BC, Jumong became the first king of the Goguryeo, and reunited all of the five tribes of Jolbon into one kingdom and he was married to So Seo-no, who is daughter of Jolbon's chief.
Split into simpler sentences: In 37 BC, Jumong became the first king of Goguryeo, and reunited all of the five tribes of Jolbon into one kingdom. He married So Seo-no, who was a daughter of Jolbon's chief.