i agree with the first part of your explanation but in the last story he didn't mean to come off as a jerk. If he liked him of course he wouldn't want to be known as his brother cause then it would be weird if and when they dated.
For the second story.... its probably the age gap that made the seme so confuse with his feelings. Afterall, he was desperate to get Kei-kun to notice him but not only did he not notice him as a potential lover, he treated him like his younger brother. I think it leds up to the seme's lack of communication and expressing his feelings for the Kei-kun
I don't like the middle brother at all, obnoxious ass. And the last story was lame. The kid was such a jerk to the guy...so yeah why would you like him??? The mangaka should learn what "cool" means cause that guy is definitely not it.