That the wife of Alaric was the sister of Ataulphus (Atawulf) of the Visigoths was stated by Langer on page 135, in his history of the Roman Empire to 527 AD. "410AD - Alaric sacked Rome, and died soon after in southern Italy. His brother-in-law, Ataulf led the Visigoths into Gaul 412 AD and thence began the conquest of Spain from the Vandals (415AD).
King of the Visigoths from 410-415, Athaulf was the brother-in-law and successor of King Alaric I. He married Galla Placida, daughter of the Roman Emperor Theodosius I who divided the Empire on his death in 395.