Arnuwanda became a king by marriage. His wife was Ašmu-nikal, daughter of king Tudhaliya I. He became a successor of Tudhaliya as his son-in-law. He began his reign under a co-regency with Tudhaliya. His campaigns include an unsuccessful expedition against the kingdom of Arawa.
Arnuwanda's parents are not known. He was a son-in-law of Tudhaliya and Nikal-mati. He had two sons, prince Ašmi-Šarruma and king Tudhaliya II. There is a very fragmentary text in which Arnuwanda names his son Tudhaliya as his future successor.
^King (lugal) of Tarhuntassa (Bryce 1997, p. 296); apparently later Great King of Hatti (Bryce 1997, p. 354).
^Nerikkaili married a daughter of Bentesina, king of Amurru (Bryce 1997, p. 294).
^Two daughters of Hattusili III were married to the pharaoh Ramesses II; one was given the Egyptian name Ma(hor)nefrure. Another, Gassuwaliya, married into the royal house of Amurru. Kilushepa was married to a king of Isuwa. A daughter married into the royal family of Babylon. A sister of Tudhaliya IV married Sausgamuwa, king of Amurru after his father Bentesina. From Bryce (1997), pp. 294 and 312.