I found the longer version of that story. Aparently the brother is forcing himself on the omega , its starts because of blackmail cuz he was searching for the blind guy's supressants and he can't tell the truth to his husband(the blind guy). And there is a plot twist. But its a spoiler. If u search [BL Short Story Collection] Obscene lnvasion (Yaoi) , u can find the whole story.
Oh yea! I actually ended up searching for the other chapters after reading the current one in this site, I was surprised when the mc got pregnant after while the three of them had sex XD
Ok, I'm usually open minded with stories but it breaks my heart to see the blind ml get cheated on and the mc didn't say anything :((