The Fey beasts from the Fey Beast Tamer background all have an Aura 1 power. (that means they affect the squares around them). This is defined by the beast, not the background, so their entries are the source material here.
And yes, they count as allies for flanking.
Your fey beast companion is considered an ally of you and your allies. It can be affected by powers in the same way that any other creature can be. It has animal intelligence, so you can communicate with it only at a basic level (like a trained pet), and it doesn’t understand complex ideas.
Lastly since not everyone has DDI, this is all from Heroes of the Feywild pp106-107.