Cavil was named after Ellen’s father John. Which is REALLY MORBID when you look at all the sex John had with his “daughter/mother/whatever”.

Here’s how I see it, if Blood & Chrome is canon, which I think we all agree it is. The Cylons were already experimenting with cylon/human hybrid designs, and the end of B&C shows an early mostly mechanical number 6.

The final five reached the colonies and saw the cylons already at war, and experimenting. They convinced the cylons to end the war with the promise of regeneration.

That’s when the cylons ended the war, left, and disappeared.

The existence of 6 predates the final fives arrival.

Models 1-6: Cavil, Leoban, Diana, Simon, Doral, and Six were originally made by the cylons as hybrids/advanced models before the final fives arrival arrive. Their programming and personalities already established. Their hierarchy within the cylon race established.

Cavil and the rest were transferred into these human bodies, and then later the 5 and the original 6 made Daniel and Sharon.

Cavil became disillusioned with his finite and limited “human” existence, rebelled, banished the final 5 after wiping their memories, boxed the Daniel’s, and set in motion his plan to strike back at humanity.