That would be Nick and Adalind, since they are a family now. Not to mention at the end too, Diana really warmed up to Nick, they were the only ones that knew what happened. So its not a surprised that Diana will call Nick dad. Also not to mention that Diana lives with Nick and Adalind at least its her primary place.
That must be an extremely powerful wesen/s that they are going to fight. Cause with the Burkhardt/Shade family (aka the most powerful family in the "wesen world") with the staff and plus the tipplets?