"I am vengeance. I am the night. I am the bookkeeper."
"What?"
"My father is DEAAAAAAAAD!"

All of us are direct descendant from people who lived hundred thousand years ago. that include all the members of the cast.

Taking into account that by about 500 BC she was a little girl already educated enough to tranlsate Greek texts, she must be at least in her late fourties by now (about 460 BC).
So she must already have given birth to somebody or she must have/gain access to a non-natural procreation method.
Otherwise her bloodline is already been cut off.

Let's see, there are 2480 years from 460 BC to 2020 AD. That are roughly 100 generations. According to mathematical model in a poupulation of a constant size of 1 million will need about 35 generations until all individuals share the same set of ancestors (meaning everyone of the first generation will be the ancestor of all present individuals or of none of them).

Of course we are talking about a growing European population of about 30 million by that time but I think it's safe to assume that the whole (human) cast relates to Allie or none of them
The same must be true for Symachus.

Perharps it's a first-born-thing, which would make the bloodline thing much more exclusive...