SOOOO cute. Jack and Rucy do this for each other too. Jack is also a very gentle dominant.
Rucy can be a little grumpy and he puts up with her moods, but if she gets really out of hand, like tries to push him out of the way, he'll give her a little charge and she backs down right away. (He is double her size)
Most of the time they groom each other and he loves to be with her all the time. He'll even do binkies when she returns from exploring without him.
Such a cute greeting!