You touch on something that has been discussed a few times.
I think in the early stages the Vampire Courts were similar to World of Darkness...vaguely related but quite different and not necessarily friendly.
I mean, humans are not that different and we don't all get along. And anyone who thinks we would all join hands in the face of an existential threat hasn't been paying attention. Like the White Court, some would use it to get advantage and settle scores. Some would try and organise everyone provided they were in charge. And some would isolate and let the others take each other out and only look after themselves.
So while they may share a similar origin, I believe the lack of unity should not be a surprise unless a strong leader forced them to work together. So far, only Drakul seems like he could do it and he doesn't seem interested.
I am not certain Drakul is the origin of all the courts (although I used to think so). His adherence to the more European/Black Court style suggests he isn't the origin, or he should have displayed traits of the other courts no?
But I do think all of them are related to the Outside...somehow. The descriptions and language used is a massive hint. The Lords of the Outer Night/Outer Dark, the description of empty darkness "empty night", the white's using that phrase, the use of Outsiders by both the Whites and Reds, Vampires showing up when Outsiders are involved, Drakul being a starborn and being involved with the stars and stones, the knowledge of Mordite by Ortega (which is meant to be a secret), Lord Faith's summoning of Outsiders and his unusual magical protection, and many, many other things.
I wondered recently if the Red King and his Lord's of the Outer Night were starborn too. Interestingly the paranet papers suggest that they fed off dark gods and became became godlike. But it's only a possible explanation. If they are starborn though perhaps it explains it... although we don't know how you go from Harry and Listen to that...
Harry notes Drakul is far stronger than the Lords of the Outer Night, perhaps stronger than them all combined.
And you're right, Lord Raith is unlikely to be the first White Court Vampire, and likely he is a close descendant if not immediate family member of the original. I suspect the original is dead as the Whites seem to be fairly political and probably killed their progenitor.
Also, an interview after Battle Ground changed the origin of the Black Court and seemingly rectifies apparent contradictions from previous statements. Originally Harry says that the Black Court have been around since the dawn of human kind. Then Ebenezer says that Dracula, son of Drakul, joined the Black Court as some sort of teenage rebellion. Jim then said in an interview several years ago that Dracula wound up turning himself into the first Black Court Vampire in order to impress Drakul, but it didn't work out. Then Jim comes out after BG when asked about this contradiction and said that Drakul created the Black Court and always had a small crew of superstars around him but then Dracula decided to expand it during the Middle ages and turn it into a a huge Court which lead to everyone getting resentful and killing them. Drakul clearly just kept on doing his thing.
My take is that Dracula was Drakul's human child, a scion perhaps, but in trying to impress dad became the more familiar Black Court Vampire and Drakul was very unimpressed.
Also apparently Drakul and Dracula have both existed long before their historical counter parts under other names in history, the basis for other monsters even.
