The literal connection in the series is that the final 5 came to the colonies and gave the cylons reincarnation in return for stopping the war. This is not the theme they were intended to represent though. They are the embodiment of the thesis of the show - that humans repeat their mistakes over, and over and over again, and the universe is in cycles. They also represent the mistakes of humanity coming back, literally in this case, to haunt them.
Who created the final 5?
No one. They were born. Their race of cylons, however, were created by humans thousands of years before the run of the show.
Are the final 5 connected to the creation of the 7?
Kind of. The modern cylons were well on their way to creating skin-jobs. The final 5 just helped them along.
And the Toasters?
Literally treated as pets by half the skinjobs, and as equals by the others. Ostensibly, the toasters created the skin-jobs, but the skin-jobs had a 'divine blessing', and gained prominence. It should be noted that most of the spacecraft fall into the toaster category, with the exception of the basestars, which are looked at as a kind of oracle.
Timeline
This is what happens before the mini-series begins, and should provide some insight.
Sometime earlier than 152,000 years before 2014
Humanity lives on the planet Kobol in 12 tribes. 837
They create cylons. The cylons revolted, and the planet kobol is abandoned. Humanity goes to form the colonies, and the cylons go to earth 1.
Sometime between 152,000 and 150,050 years ago
The cylons on Earth 1 create another race of cylons that revolt. 5 Cylons rediscover reincarnation, just as the bombs start to drop. They travel back to the colonies, going at just below light speed, showing up at the colonies... we will get to that. <PERSON> also write "All along the watchtower." <PERSON> fails to give credit.
150,050 years ago (50 years before the show)
<PERSON> steals some technology and creates cylons again...out of his daughter.
Circa 150,025 years ago
The Cylon revolt is well underway. They are already developing skin jobs. The final 5 arrive and convince the <PERSON> to end the war, and give them reincarnation.
150,000 years ago
Number 1 wipes the memories of the final 5, and starts another war with humanity. the series begins. 837