Don't get this German vampire mixed up with the Doppelganger. They are very much different. Doppelsauger is German for "double sucker". Consider it's obsession with breasts, the name seems to fit.
He is believed to be the revenant of a child who sucked his mother's breasts after being weaned onto solid food. If this particular type of child dies, they would consume the flesh from their breasts while in their graves. Then it preys a member of their family, draining the life from them and eats their breasts.
There are certain preventative measures you can take. Place a coin between the teeth of the corpse. Place a semi-circular board under the chin of the corpse. Then, make sure the burial garments are as far from the lips of the corpse as possible.
Source: Monstropedia and VampGirl.com