The "bad guy father" you say is the first homunculus, born by the blood of hohenheim. So, yes, the people of xerxes, who already were discovering and studying alchemy, created it.
Then y didn't d people of xierxer(king & his underlying ppl) know how to become immortal?when it was them who created it (bad guy"father")?
Alchemy was a science studied since medieval times (btw, irl), and like a science, it needs to be discovered step by step. Xerxes alchemists eventually created the thing on the flask through large investigations (maybe). And the thing on the flask gave to them the 'secret' of immortality.
Idk if I'm explaining it properly, sorry.
(i know it's from 2 years ago, but I want to say something as well.)
The first homunculus didn't really have a connection to Hohenheim, since it only copied the physical form of hohenheim. Hohenheim achieved his immortality because he was one of two person (the other is the homunculus in the flask) standing in the center of the circle (just like what the corrupt military bosses tried to achieve, when one of them panicking and said, "i cannot be here, please bring me to the center")
So there's no blood relation between the two.
But didn't hoenheim's master or whoever that was used his blood?
Actually yes, thanks. The master used Hohenheim's blood to create, or at least bind to the plane, the first homunculus, aka, the thing on the flask.
After all this time, I still have my doubts....How did the bad guy "father" came to exist in that bottel?
Did the humans from xierxer created him?
Did the alchemy came from him or was it already existed before only and was used to create him"father"