He didn't sleep with the father. In one of the past chapters, Eugene revealed that the one he actually slept with was Winston, but he doesn't remember because I think he was drugged or in rut or both. I don't remember clearly, but yes, the child is Winston's, and that's why Eugene has been trying to hide the fact of it, because then the will would automatically be fulfilled, and he doesn't want that. 
As for why the father was good to Eugene, it hasn't been revealed, but based on Eugene's memories, he was a good man without any indecent or vulgar behavior towards him. (It was the mother and the other family members who have been feeding those ideas to Winston because they don't like Eugene at all.)

Another one to the end 😭🫰🏻

Maybe he's acting... PLS DION I ADORE HIM DONT END UP DEAD BC YOUR STU** AS* ENDED UP VILLAIN

I was listening to "Freak" by Sub Urban, and exactly at the end, it fitted so well! LMAOOO

I cant... this is too much...

I THOUGHT WHAT EVERYONE ELSE THOUGHT, RIGHT???

As a Spanish speaker I can really imagined Taeyi singing "Besame mucho" AND THATS THE MOST SENSUAL THING!!!😭🔥

Will miss them! It's such a lovely manhwa, sadly it ended too fast!

AHHHH DOYOON NOONAAAAAA!!!! I love him sm!

IM LOVIN THIS SO MUUUUUUUCHHHHH BWT ALWAYSSSSS BRINGS SUCH MASTERPIECES THEY NEED AN AWARDDD PLEASEEEEEEEEEEE

Now again with the tricks...

I'm so confuseddddd with the tree family of these 😮💨 can someone care to explain to me why first they were brothers by blood? Cuz I thought both have different parents? But the 2 couples were brothers with different wifes? So from the very beginning they should have been cousins right? So why always mentioning they were brothers???? WAAAAAA IM RLLY RLLY CONFUSED! and now they really are cousins and not by blood my mind is going to blow up.....

WHAT IN THE CORNCOB IS THAAAAAAAAATTTTTT?????

NUUUUUU I WANTED MOREEEEEE SIDE COUPLEEEEEEEEE 😭😭😭😭😭😭 anywaysssss I love it such a good story 🥹💕✨️

Be right back I'll go cry in a corner:')