theory : uke himself doesn't know that , he just has dreams about his past life plus i don't think his past life lived it's clear that the seme in his previous life married and get a child ( in case if the child who looks like him and the woman are his wife and son ) and after that the uke died maybe that's why destiny blessed them with a child ( which they needed to have in past life to be together but couldn't ) and a good health ( since maybe he died cuz of ilness )
W8 wut? So that 1 with some kind of ancient korean setting is kind of like them...?
I think it's just a dream, like the ones Hosik had before where he was the servant and his husband was the master.
In the latest raw are they both reincarnated, and does seme knows about it?! Thank god everything turned out find.