The band around the sixth volume of Hajime Taguchi's light novel series, Kono Naka ni Hitori, Imouto ga Iru! (roughly One Among These, Is Your Sister!) announces that the previously announced TV anime adaptation will premiere this July.

Source: http://twitpic.com/8z8fcg
It also announces that the series will be animated by Studio Gokumi (A-channel, Koe de Oshigoto) with Munenori Nawa (R-15, kiss x sis) directing, Gou Zappa (Koihime Musou, Hoshizora he Kakaru Hashi) doing series composition, and Kenichirou Katsura in charge of character designs and overall animation director.

Source: http://twitpic.com/8zggxf
The story is a love comedy about Shougo Mikadono, who is attending school and trying to find a girl to marry there as a condition of inheritance. However, as the title suggests, one of the possible girls is his sister.
Update: The official website is now open with a key visual and asks... "Who is 'IMOUTO'?"
Source: @IEEE80211 via 0takomu (Date, Staff)
Image ©Hajime Taguchi/Media Factory
Previously: "Kono Naka ni Hitori, Imouto ga Iru!" Anime Announced