I want

Sigh...i would hate that imagine how Alex would feel that his brother once again takes something away from him omg

But it will be interesting when Alex has self esteem and confidence in himself.. Alex will realise his potential and try to win DG back.. That will be first win from his brother.. I think Alex has a complex about his brother so if this plot happen, Alex can move on from that complex

I won't say it's impossible, but it's unlikely that will happen. One, I think it's kind of overdone to have every single thing become a rivalry between the brothers. Plus it's established that the rivalry isn't so much Jihoon and Jiwon, but Jiwon and his parents with poor Jihoon caught in the middle. He's not even given a face because he's considered so much more handsome than Jiwon. This isn't how you characterize someone who will play a big role in the story. Even the ex, who eventually had his face revealed, played a minor role in past events.

Two, Jiwon himself admits that his brother actually is a good person and has never intentionally tried to hurt him. He just never stood up for him to their parents because he valued their parents' approval too much. For him to compete with Jiwon to get DG would be out of character.

Three, Jihoon doesn't seem to be gay which I think Jiwon would have mentioned by now if he was. The ex had a hard time doing anything beyond using Jihoon for money and clout, which tells me that the ex either thought he couldn't get away with hitting on Jihoon without causing an issue, or he tried it and was turned down.

And finally, we're about 3/4 of the way through the story, Jiwon lives apart from his family to the point where we've only met them in flashbacks, and the main issue of the plot is how the main couple are going to get back together, not who is going to come between them. Bringing in Jihoon now means there would have to be a rushed resolution. Jiwon's self esteem was never about his brother. It was about his parents' perception that he wasn't and would never be as good as his brother. His brother was also a victim so I'd be disappointed if Mingwa used him to poke at Jiwon's complex when the brothers were both used and abused by their parents in different ways.