Owain is first securely attested in 934, when Æthelstan invaded and ravaged the Scottish Kingdom of Alba and seemingly Strathclyde as well. In the aftermath of this campaign, both Owain and Custantín are known to have been present at Æthelstan's royal court, witnessing several charters as subreguli of the Englishman. Three years later, the Scots and Cumbrians allied themselves with Amlaíb mac Gofraid against the English at the Battle of Brunanburh. It is possible that Owain is identical to the unnamed Cumbrian king recorded to have participated in this defeat by the English. If he was indeed present, he could have been amongst the dead. His son Dyfnwal ab Owain is recorded to have ruled as King of Strathclyde within a few years.
For hundreds of years until the late ninth century, the power centre of the Kingdom of Al Clud was the fortress of Al Clud ("Rock of the Clyde"). In 870, this British stronghold was seized by Irish-based Scandinavians, after which the centre of the realm seems to have relocated further up the River Clyde, and the kingdom itself began to bear the name of the valley of the River Clyde, Ystrad Clud (Strathclyde). The kingdom's new capital may have been situated in the vicinity of Partick and Govan which straddle the River Clyde, and the apparent inclusion in the realm's new hinterland of the valley and the region of modern Renfrewshire may explain this change in terminology.
The title of Owain's grandson and eventual successor, Máel Coluim, as it appears on folio 9r of British Library Cotton MS Faustina B IX (the Chronicle of Melrose): "rex Cumbrorum".
At some point after the loss of Al Clud, the Kingdom of Strathclyde appears to have undergone a period of expansion. Although the precise chronology is uncertain, by 927 the southern frontier appears to have reached the River Eamont, close to Penrith. The catalyst for this southern extension may have been the dramatic decline of the Kingdom of Northumbria at the hands of conquering Scandinavians, and the expansion may have been facilitated by cooperation between the Cumbrians and insular Scandinavians in the late ninth- and early tenth century. Over time, the Kingdom of Strathclyde increasingly came to be known as the Kingdom of Cumbria reflecting its expansion far beyond the Clyde valley.[note 2]
The title of Owain's apparent father, Dyfnwal, as it appears on 29r of Paris Bibliothèque Nationale MS Latin 4126 (the Poppleton manuscript): "rex Britanniorum".
Owain was likely a son of Dyfnwal, King of Strathclyde (died 908×915). Dyfnwal is specifically attested by only one source, the ninth–twelfth-century Chronicle of the Kings of Alba, which reveals he died between 908 and 915.[note 3] Dyfnwal's parentage is unknown, although he might have been a member of the British dynasty that ruled Strathclyde before him. He could have been a son or grandson of Eochaid ap Rhun (fl.c.880). Alternately, Dyfnwal could have represented a more distant branch of the same dynasty.[note 4] In any case, the names borne by Owain and his apparent descendants suggest that he was indeed a member of the royal kindred of Strathclyde.