Anime Description: UFO Baby

UFO Baby is a story about a baby that was sucked up by a great wormhole together with his babysitter.They landed at the Saionji temple where Miyu Kozuki and her friend Kanata Saionji (who are also most of the time thought of as lovers, especially by their classmate Christine who likes Kanata very much).

So from there, they treated Lu (baby from space) and Bow-meow (pet babysitter) as a real family member. Lu possess magical powers which only he can control. Bow-meow, being the one responsible for Baby Lu, hopes to return to their planet by waiting for wormholes time by time.

About Miyu and Kanata, well, they do all they can to keep Baby Lu and Bow-meow's secret from their friends and from anyone that goes in their temple.
Miyu's mom and Kanata's mom were best friends! When Christine heard that Kanata and Miyu were staying together in one house, then she got angry. To cool her anger, Kanata and Miyu made up a lie that they were merely cousins.

Article Source: http://www.absoluteanime.com/ufo_baby/