Complex sentence: "Udayavarman" was, most likely the same king we know as Udayadeva (the son of Śivadeva I and, later, adopted son and heir to Aṃshuvarmā), and the father of Narendradeva (Tib: "Miwang-Lha").
Split into simpler sentences: Udayavarman was most likely the same king we know as Udayadeva, the son of Śivadeva I and later, the adopted son and heir to Aṃshuvarmā. He was also thought to be the father of Narendradeva (Tib: "Miwang-Lha").