Anna bat Joseph, The Prophetess of Arimathea (Enygenus) - My 56th Great Grandmother

You're right. This is highly questionable

Beli is recorded in the Mabinogion and Welsh Genealogies as having been the father of Caswallon (or Cassivellaunus), the leader of the Celtic tribes who repelled Cæsar's invasions of 55 & 54 bc. He could, therefore, not possibly have married Anna of Arimathea. Moreover, the local ruler whom Joseph received his land gift from, is said to have been Arfyrag (or Arviragus), Beli & Anna's supposed great great grandson. (source; http://www.earlybritishkingdoms.com/articles/josanc.html)