Harem Time the Animation.

Satou Reiji's life changed when his real lineage was discovered. He is the son of a rich man who passed away recently, and now Reiji is the new master of the Kamiyama house. But there is a catch! In order for him to be accepted into the house legally, he needs to provide an heir, and in order to do that, he must choose a wife from his very own harem! (These OVA's are based on a manga by tosh.)