
I think its bec they know how difficult their son is (cant stand stupid people, domineering) lmao. Plus the aspermia diagnosis on SeungHyeon. Thats why for them, Hosik is a miracle. Maybe in their minds, if SeungHyeon didn’t met Hosik, their son would remain single and childless forever.
And this is just me, but I think even his parents are not keen to challenge SeungHyeon. Their son is a brilliant business and family man. He is actually an ideal chaebol son. Thats why protesting SeungHyeon’s choices would seem ridiculous and unproductive.

Ofc they love and adore Hosik. They respect and treasure their son. But the premise of the original comment is why SeungHyeon’s parents seems chill and accepting of his choices, giving minimal resistance to SeungHyeon’s decisions, thats why I said bec they know how domineering their son is. Bec lets accept it, SeungHyeon IS domineering. He sometimes even have a one track mind. The way he pursued Hosik is a good example of that. Thats why many readers tagged him as a red flag.
Not just his parents, I think SeungHyeon’s whole clan has an idea how obstinate and goal oriented SeungHyeon is…and how brilliant he is at producing results. In a way, those traits of his factor why his family doesn’t challenge SeungHyeon openly. They adore Hosik, who wouldn’t, but aside from that they trust SeungHyeon’s cunning and ability to get what he wants and trample those who would think to oppose him. Thats why there is a panel of Hosik telling his mother that SeungHyeon’s company has no inheritance struggle. Thats a clue that no cousin of his is challenging SeungHyeon for the heir position.
Nobody's talking about this but props to Sunghyeon parents for being so chill and welcoming Hosik with open arms and be the best cool grandparents ever.