i have the theory that it was the uke past life family, because from little flashbacks in this season, we saw that Mugo took an exam to become a political figure, Which means he had money or was sponsored by somone with money, his clothes also was different from the one the uke past life was wearing. I feel like he was the lord of the household and his servants (uke family) betrayed him to saty with his position
I think it's the opposite.
Mugo was from an influential and wealthy family while Ja Heon was a lowly Omega servant. They fell in love and Mugo cleared the exam so he had power to go against his family and take Ja Heon as his mate. Sadly Mugo's family probably killed Ja Heon and to take revenge Mugo signed the deal with the devil and took care of Ja Heon's family as compensation by granting them wishes.
Ja Heon's family soon realized that just because one Omega got sacrifice they won the favour of a Deity. So why not keep sending him Omegas, saying that he is their mate reborn, so they can keep getting their wishes. After a while they didn't want to sacrifice the members of their own family so started looking for Omegas in distant relatives. This is how the branch families emerged who provide the sacrificial Omega. The fourth entity inside Mugo who is the most dangerous and holds the memories of the previous life always believes the Omeg sent to him is his mate who is reborn but he soon finds they aren't and hence, murders them in rage. Thus, the cycle continues.
that's the thing, if he was willing or was his idea the ritual would have been different. But he was knocked out, tied, isolated, starved, mentally abused and more. We've seen that already. I think both of them died long ago, cause the mugos we know, aren't the original one, their result of the ritual, while the og uke was also murdered, cause season 1 showed flashbacks of him on the ground death

I'm telling you they're setting us up, making sure all three sides love him, then they're going to hit us with a "surprise, past uke was evil"!
Or at least I hope it will be interesting like that, because it would be weird if it was the typical sad past troupe by now