Here's the problem when we're lost in translation, or more like, romanization Since this story is originally written in Korean, people might spell every name differently with alphabet. For example 루시아 that's literally read as Rusia, but no, our FL's name here is Lucia. Besides, Rusia would've sound weird to be a female name lol. The same thing goes with Hugo/Hugh, Hue/Hiu, Damian/Damiem/Demien, etc. The point is, you just need to understand who is who regardless how their name is spelled :)
The old man is the one who recently appeared on the manhwa and is a personal doctor of Taram's head family. Meaning he was the previous duke's doctor and now he is our ML's doctor. And as I've said in this post before, Hugo is actually the name of our ML's brother who killed their father aka the previous duke. The event where the old man (the doctor) saved Hugo (our ML's bro) is another story.
Now let me say this again to make sure you don't confuse our ML and his bro. Our ML's real name is Hue, but for some reason (which you can read on this original post) our ML chose to use his bro's name ever since he became a duke. That's why our ML's name is "Hugo" now.
Which half-sister? Currently the Taram family only consist of 3 people: our ML, Lucia, and Damian. If they want the Taram bloodline goes on, of course Damian needs to have a kid with someone. However, the crazy old man is too obsessed to keep the Taram bloodline goes on as pure as possible. Therefore, he has been insisting on incest route.
Spoiler~
.
.
.
.
.
If my memory is not wrong, according to the novel, the old man and his family has been serving under the Taram family (though right now the old man is the only one left alive). Basically it has been like a tradition for him and his fam to serve, take care, preserve, and make sure the Taram glorious bloodline keep going. His whole fam extremely adore the strength, viciousness, and the cold-blood nature of Taram fam. They want to and will make sure to keep the Taram bloodline as pure as possible because the purer a Taram member's blood is, the stronger, more vicious, and more cold-blooded they would be. That's why the old man and his fam has been trying their best to promote incest relationship. So I guess he's a mad man cuz he's born and raised by mad family lol. And you might even think of him as a masochist I mean, literally There will be a time when the old man is going to be captured, quarantined, and tortured by our ML but he shows no sign of fear whatsoever. Instead, he'll look like he's actually enjoying himself and (again) adoring how vicious our ML can be that our ML will get even more sick of him
I see that there are some people who are still confused about Taram's family history, so here I am trying to straight things up. Half of this post has been explained in the manhwa, but there might be some spoiler. So please read with caution.
Let me get this straight first. Our ML's real name is Hue/Hiu. Our ML's brother's name is Hugo/Hugh. In the past, the duke wanted Hugo (ML's bro) to be the next head of Taram fam, but unfortunately Hugo (ML's bro) was seen to be too soft and not fit the position. Therefore, the duke changed his mind and made Hue (ML) to be the head of Taram. Knowing how it feels to be trapped under the duke's cruel hand, Hugo (ML's bro) killed the duke to set Hue (ML) free and then killed himself so that Hue (ML) would be the only person who can fit the position. However, before Hugo (ML's bro) did all this, he sincerely fell in love with a woman and had a kid wih her. He didn't knew that the woman was his half sister and yes, the child is our Damian. After all that killing happened, Hue (ML) took the position as the head of Taram's fam under the name of "Hugo" because he still thinks his bro didn't deserve what happened to him and because he hates himself for not being able to save his bro. Plus, "Hugo" (our ML's current name) also took Damian in as his son cuz he couldn't abandon the child of his beloved bro. From here on out, our ML has been living his life as "Hugo". No one else knows about his true self and the history about what happened except himself and that old man. Eventually "Hugo" will tell Lucia about what happend and they both decided not to tell Damian about his real father until he's grown up.
I hope this long rant clear things up for those who's still confused about the Taram's family history and Damian's background. If there's still something you're confused about, feel free to ask.