Hajime Taguchi's light novel, Kono Naka ni Hitori, Imouto ga Iru!, will be getting an anime:

Shougo Mikadono's father, CEO of the large international company Mikadono Group, dies and leaves the company for his son to inherit on a couple conditions. He has to pass muster by taking a year of special training at the company, but he also has to attend his dad's alma mater and find a girl there to marry. However, it turns out Shougo has a half-sister (same father, different mother) who is attending that very school and is aiming to marry him. He finds this out, but since he isn't sure which girl is his sister, well...
The light novel series had its fifth volume released this past August. We'll be on the lookout for further anime news!
via Yaraon!