A younger sister is raised in a different household due to parents' divorced, and only meets her older brother later when they are both teenagers. Anime focuses on a harem around the older brother but in the last episode she declares herself as a romantic candidate for him too.

I remember this was a show, I think around 6 or 13 episodes which I had watched in full several years ago, but I forgot the title of it. It was not explicit like Yosuga no Sora or serious like Koi Kaze, it was this cutesy wincest fanservice thrown in during the last 5 minutes. Previous to that it was just the usual jealous imouto routine.

Unfortunately I cannot provide a picture to help, just hoping this triggers recognition in someone with a better memory.

-Ty

I'm sure it Kono Naka ni Hitori, Imouto ga Iru!