They cluster both with Iberians and French Basque, as is to be expected, but there's an amazing amount of structure even within the villages, resulting in high runs of homozygosity. Lots of drift because of isolation, is also to be expected, and the date for population formation is about 2500 years ago, or about 500 BC, before the Roman Era or Islamic Invasions.

See:

https://www.nature.com/articles/s41431-021-00875-0


"The area of the Spanish Pyrenees is particularly interesting for studying the demographic dynamics of European rural areas given its orography, the main traditional rural condition of its population and the reported higher patterns of consanguinity of the region. Previous genetic studies suggest a gradient of genetic continuity of the area in the West to East axis. However, it has been shown that micro-population substructure can be detected when considering high-quality NGS data and using spatial explicit methods. In this work, we have analyzed the genome of 30 individuals sequenced at 40× from five different valleys in the Spanish Eastern Pyrenees (SEP) separated by less than 140 km along a west to east axis. Using haplotype-based methods and spatial analyses, we have been able to detect micro-population substructure within SEP not seen in previous studies. Linkage disequilibrium and autozygosity analyses suggest that the SEP populations show diverse demographic histories. In agreement with these results, demographic modeling by means of ABC-DL identify heterogeneity in their effective population sizes despite of their close geographic proximity, and suggests that the population substructure within SEP could have appeared around 2500 years ago. Overall, these results suggest that each rural population of the Pyrenees could represent a unique entity."

The largest amount of haplotype sharing, however, seems to be with the Basques, followed by Sardinians, and then the Spanish.