A further pair of stones lies to the NW of the stone row. They are marked on the OS 1:25000 as a pair of black dots, but not labelled.
Details from Coflein:
coflein.gov.uk/en/site/261687/details/RHOS-Y-GELYNNEN%2C+STONE/
coflein.gov.uk/en/site/261668/details/RHOS-Y-GELYNNEN%2C+STONE+II/
[NB: “Stone II” is standing, see photo.]