Upvote:2
Abd al-Rahman I's mother was a Moor from a tribe called Nafra (click the link for pg 111). That helped him to be recognized first in Morocco and then in Islamic Spain as well.
Upvote:10
Peter C. Scales:The Fall of the Caliphate of Cordoba: Berbers and Andalusis in Conflict (Medieval Iberian Peninsula, Vol 9), the source linked in the answer by @Mr.lock / @Kobunite
actually hints at a plausible answer to OP's question, namely that
Relaying accounts by Muslim historians Scales says (p112) that already in 121AH/739AD some 30,000 soldiers, among them 10,000 Umayyads, had been sent westwards by Calpih Hisham.
A vanguard of this detachment, some 7,000 Umayyads, found themselves besieged by Berbers in Ceuta, and appealed to the governor of al-Andalus to be allowed to cross the Gibraltar.
As he agreed these 7,000 would become the second wave of Arabs to settle in Spain.
So when Abd al-Rahman landed in al-Andalus 755AD he would be able to count on the support from his own kin.