Kiaora from Aotearoa ,
I know this is a bit late , but i just signed on and yours was the first post i came to that i could help with
Rhiannon didnt but her brother Morfran did .. He was famous for it !
his horse was Guelwgan Gohoewgein . (silver white , proud and fair ) .
Have a few sources , notes and storys if you need them ..