I think, in a way, Nanmu's wish of having a wife and a child (basically having a proper family that he could call his own one day) got fulfilled in a twisted way. The relationship he currently has with Pil-Gyun fulfills his both desires. Pil-Gyun is both his lover and, in a sense, his child too. So, Nanmu is essentially getting both relationships from Pil-Gyun.
I think thats why author kept the 'Dad' thing till the end as well.
I think, in a way, Nanmu's wish of having a wife and a child (basically having a proper family that he could call his own one day) got fulfilled in a twisted way. The relationship he currently has with Pil-Gyun fulfills his both desires. Pil-Gyun is both his lover and, in a sense, his child too. So, Nanmu is essentially getting both relationships from Pil-Gyun.
I think thats why author kept the 'Dad' thing till the end as well.