Claudius (1 August 10 BC – 13 October AD 54, emperor from AD 24) occupied Britain in AD 43. As part of his pacification program, his eldest daughter Genuissa (Venessa Julia) Claudia married a Briton king, Aviragus (Arviragas Arfyrag). Those two had a son, King Marius, whose son in turn was the aforementioned Old King Coel. As you recall, Coel was an obedient vassal of Rome, and had probably been educated there before becoming king. Turns out he had Roman blood, Emperor blood even, and so have we. Coel was the great-grandson of Claudius, and all of us relatives are approximately 65th great grandchildren of this Roman Emperor. There is also Claudius’ maternal grandfather, Mark Antony, at around 67th.
All these connections are made in all the sources I have consulted, without significant controversy. If I selected certain of the “alternate parents” suggested for some other descendants, I could reach Julius Caesar himself, plus the Biblical Joseph of Aramathea. But I did not, and so we are stuck with “only” Claudius and Mark Antony.