The Venicones were a Celtic tribe inhabiting the area now known as Fife in Scotland. "Unfortunately for the Venicones, they occupied the very region that the Romans needed to invade several times in order to quell attacks by Britons (Picts) in the east of the Highlands, including attacks by the 'Pictish navy." Fleeing the Roman advances by sea, some of the Venicones may have resettled in Donetal, Ireland, and Gwynedd, Wales. 
A legionary fortress was built at Inchtuthill, Tayside (Pinnata Castra), which remained occupied during the late first century by the Twentieth Legion Valeria.
Tacitus ap Cein, "Tegid", son of (Gwr-)Cein ap Doli, flourished about the year 270. ref name="venicones"/>
Wolcott observes that review of the most ancient manuscripts suggests the omission of some generations, and Tegis is actually the son of Iago. 
Williams adds that Tegid ab Iago is named the father of Padarn Beisrudd in the biographical dictionary Enwogion Cymru.
Padarn (Beisrudd) is said to have been a hermit and bishop. "Pais Padarn Beisrudd" or the coat of Padarn with the crimson coat, was onew of the thirteen beautiful specimens of workmanship of the Isle of Britain. (See Jones's Bardic Museum, 48) 
Harleian MS 3859 names Patn pefrut, child of Tacit, child of Cein; material from Jesus College MS 20 and Hengwrt MS 33 indicate that there are two more generations, Iago and Gwyndog, between Tacit/Tegid and Cein.
(O)uen map (H)iguel map Catell map Rotri map Mermin map Etthil merch Cinnan map Rotri map Iutguaul map Catgualart map Catgollaun map Catman map Iacob map Beli map Run map Mailcun map Catgolaun Iauhir map Eniaun girt map Cuneda map Ætern map Patern Pesrut map Tacit map Cein map Guorcein map Doli map Guordoli map Dumn map Gurdumn map Amguoloyt map Anguerit map Oumun map Dubun map Brithguein map Eugein map Aballac map Amalach, qui fuit Beli Magni filius et Anna mater eius quam dicunt esse consobrina Mariæ Uirginis Matris d’ni n’ri ih’u xp’i.
Tegid appears in a pedigree of Pughe, of Mathavarn, in Cyveilog, reaching back to biblical Adam, presented by Lewys Dwnn. The pedigree illustrates the fondness of the Welsh for pedigrees as well as the difficulty of determining at what point the pedigree moves from history to legend. 
The pedigree of Pughe also appears in a work by the Powys-land Club.
The complete pedigree is presented and discussed at Space: John Pughe's Descent from Adam
According to Darrell Wolcott he should be Tegid ab Iago rather than ap Cein.
Have you taken a DNA test? If so, login to add it. If not, see our friends at Ancestry DNA.
Tegid is 47 degrees from Isaac Asimov, 51 degrees from David Attenborough, 49 degrees from Bill Bryson, 44 degrees from Richard Dawkins, 51 degrees from Bengt Feldreich, 55 degrees from Ruth Gates, 46 degrees from Stephen Hawking, 59 degrees from Julius Miller, 46 degrees from Bill Nye, 52 degrees from Magnus Pyke, 52 degrees from Carl Sagan and 47 degrees from David Randall on our single family tree. Login to find your connection.