Beli Mawr is claimed as the head of the House of Gwynedd by the line of Cunedda Wledig, founder of the Kingdom of Gwynedd, following the End of Roman rule in Britain during the late 4th century under Magnus Maximus.[8] The pedigree is shown in the Harleian genealogies, the oldest documented genealogies of Welsh royal families.[8] In Welsh legend, according to the Welsh Classical Dictionary, Beli Mawr was born between 120 BC and 80 BC.[9]