They were most mighty under King Priam when he wrested Troy or Wilusa from the Hatti.
Going that far back into pre-history you get myth at best. It is interesting insofar as it informs what the Britons thought of themselves, but in order to (re-)create a monarchy? Nah, not useful at all.
I think Wales is going to be with a High King again. If an heir male line is down from Cunedda with no female breaks, the High King's Seat can be reestablished. I wish I knew the YDNA of King Cunedda.
Again, too far into pre-history and wishful thinking. Plus you need a sexy story to get people interested. We've either got die hard republicans (Plaid), Die hard Monarchists who love Liz, Charles, Wills and you're not going to convince either of those sets I don't think. So it's everyone else and to get them you need to give a convincing reason!
We know that the House of Aberffraw (and a few other Kingdoms) existed and theoretically a male (undisputed) line heir and possibly a female line (you can see from this thread that it's disputed) could possibly claim that it was there's by rights. It's been done before – see the Sir John Wynn.
It's a story that the we could grasp and appreciate; Llewellyn the Last killed by the English, his daughter imprisoned for life, his brother declared King and within 6 months captured and became the first person of noble blood to be hung, drawn and quartered. The English king offers our people a Prince of Wales who speaks no word of English and then presents his baby son, taking the piss out of us. The English Kings have always claimed ownership of the title “Prince of Wales” and given it to their heirs on this right of conquest, Charles took the House of Aberffraw's coat of arms as his own and put an English crown over it.
The House of Aberffraw were the last dynastic, native Royal House in Wales and ruled for over 700 years. One of their descendants claims it and it's sexy.
We know that Owain Glyndŵr fought a rebellion and controlled much of Wales. He's our William Wallace and Robin Hood rolled into one. Universities have been named after him, statues built and his coat of arms is seen at sports stadiums and a symbol of independence. Even republicans revere him. One of his descendants claims and it's sexy.
A welsh Lord or Baronet or something who's family has been posh and lived in a castle for a few hundred years is made King? Let's be honest, we'll probably forget he had no right to the title and it was an English king who made is ancestor Lord whatshisface. It's still sexy.
DNA test to show that you're in the male line of a possibly mythical person and your ancestors once ruled Troy? Not sexy, no resonance with your average man on the street either in the valleys, the cities or up north.
Plus, you're never going to find DNA tests that show decent from Cunedda as he has no known male line descendants. You'd need at least 2 known lines with no infidelity in order to find or verify others.
Is it true that the first clan of Wales is Cunedda? I found that in an old book and wondered if it is consensus today?
Not even close. Maybe they mean the pre-eminent royal house? In that case I'd say they may have a case.
Cunedda probably existed but some people think his name might have been given retrospectively and that it was a title. He (or the person/people he represents if he's a myth) came from within the Roman walls (or just outside on the Pict side) between 350-450 AD. The Romans used the space as a buffer state or a semi-autonomous province.
Cunedda's father, grandfather and great grandfather all had Roman names and were probably professional Roman soldiers, possibly of British decent. His grandfather was certainly a commander over part of the land past Hadrian's wall and the assumption is that command passed to his son and eventually his grandson Cunedda. It is possible that they were British chiefs who the Roman's tried to butter up by giving imperial rank, but unlikely IMO in that Cunedda's great-grandfather wasn't a Roman commander but still has a Latin name.
He travelled with a warband and drove a certain Irish/Pict tribe out of north Wales. There's also evidence of him fighting in South Wales (a hill name).
That's pretty much all we know. Geoffrey of Monmouth claimed a lot of other stuff, but you have to be really careful with him and assume that it's more likely to be fiction than fact.
There were already welsh tribes in Wales before Cunedda and they stayed after he settled. They were there when the Romans first invaded. No clans. Tribes and Royal Houses though.