...oh God. Pfil, I'm so sorry.
Anyway, a few more:
-The Lecardes are descended from the non-Mathias side of the Cronqvist bloodline. That's why they can unlock the VK's power for non-Belmonts (the Whip of Alchemy being a product of Cronqvist magic) and that's why Alucard gave them the Spear.
-Trevor wandered much of Europe and parts of Asia pre-CV3, killing all kinds of monsters along the way. He may've made it as far as India and gotten a taste for the local cuisine. That's why his second drop item in COD is... curry.
-In Bram Stoker's Dracula, Van Helsing says, "For in this enlightened age, when men believe not even what they see, the doubting of wise men would be his greatest strength. It would be at once his sheath and his armor, and his weapons to destroy us..." The Belmonts may have realized this decades earlier (as the world was getting more and more modern) and it might've been one of the reasons they disappeared. Though it still wouldn't explain why they can't use the whip till 1999.
-Speaking of Van Helsing: he helped train John Morris and is from the second best vampire hunting clan of the Castlevania universe.
-Similarly, Maxim had a hand in training young Richter.
-That scarf Richter wears in DXC? A lady's favor from Annette.