There is the uke and the seme, they are stepbrothers and the uke is older. Uke lives alone, he didn't meet with his brother since years, and when his brother graduated from high school, he went to the uke's place to live. Seme loves uke, but he doesn't realize it, and he act really seductive.
For example: uke went to shower but he forgot bring cloths and he came out naked (or with just a little towel I don't remember) and when the seme see him he shouts and scolds uke to put on something he can't walk like this (and secretly the seme is really turned on) and the uke don't understand what's the seme's problem.
I remember the seme is very posessive and jealous. I'm not sure but maybe one of them is model.

Do you know which manga is it?

Toshishita no Ryuugi

That's it! Thank you 😀