
I think what Idea is referring to is Seolhyun's split personality, and the child. Idea said twins (meaning seolhyun and the dark wolf-a fragment of him, himself)
So in total the ones in danger would be
(1) Seolhyun's Human side (which is made to believe he was a male)
(2) Seolhyun's Lycan side (which knows it was a female)
(3) Seolhyun's child
Anyways, that's just my understanding so I could be wrong. ╮( ̄▽ ̄)╭

Seol is expecting indeed 3 babies.
One is different while the other 2 are twins. Why this setup, I had no idea back then in the raw, and have even less now.
Reasons why they might be in danger:
- the 2 different personalities Seol possesses a human male mind and a Lycan female mind. They might be a burden at this point for the babies
- the fact that he is a mutant female Lycan (a result of two female lycans mating)
- Hwa being a hybrid (lycan+ vampire).
Also, because the human side of Seol thinks is a male, it might have a burden in his pregnant state, something that I think that it goes along with what Ino stated.
So yeah, until we find out to what extent the hypnosis that Ino used on Seol, we won't know how to save them.

I don't if that was the case and I don't know If I'm right. Either way, 1 or 3 kids will be cute since Hwa and Seol are cute UwU
, but I'm leaning more to one kiddo, since I distinctly remember Leebin said 'Child' NOT children.
I couldn't quite understand what you're pertaining on your statement, but my stand (again I don't know if I'm right) would be that he has ONE baby, and the twin Idea is pertaining to-would be Seolhyun's fragmented personality(the human side, and the female lycan side-the phantom wolf)

My understanding came from the raw and Spanish translations (they confirmed the number). They are quite around the climax of the story. And yes, no matter the number of babies, we'll be happy. However, some things in this last chapter were not translated as accurate as of the previous chapters.
And I was trying to explain some of the factors that may kill those babies.
One of the main threats to those babies might be their belonging to different species. Like Hwagok almost died when his blood (lycan) and Hwa Lee (hybrid = vamp + lycan) mixed when he was giving birth.
Wait wait wait.. TRIPLETS?!?!?? Like damnnn a-and
w-what? They're near death?!?! Noo, i want to see their babies