- "Marcus's life changed dramatically when Aro brought home his newly turned younger sister, Didyme, along with the first members of the guard - vampires who were drawn to Didyme's aura of happiness. None of these early subordinates lasted more than a few centuries; they were still experimental at that point. Didyme's gift had always been with her, though subtler during her human years, and so she was used to many suitors."
- ―Entry on Didyme's gift[src]
According to Stephenie Meyer, it was only shown by Didyme, Aro's sister, which made the Volturi members around her happy during her time of existence. But the most benefactor of this talent of hers was Marcus, one of the Volturi Leaders, who became her mate.
The Aura of Happiness also can bring happiness to the beholder, as well as those around them. However, Jasper's emotional manipulation, can only control the emotions of others.