I thought that the Irish are genetically related to the Spanish. There were obviously waves of tribes pushing west into Europe, with the people at the fringe (Ireland and Spain) most likely to be genetically similar to the earliest groups.
I believe the Basques are closely related to the Celts. A lot of the Spaniards are also Germanics (Visagoths). Probably a mix of Celts and Visagoths.