  We consider rate-distortion with two decoders, each with distinct side
information. This problem is well understood when the side information at the
decoders satisfies a certain degradedness condition. We consider cases in which
this degradedness condition is violated but the source and the side information
consist of jointly Gaussian vectors. We provide a hierarchy of four lower
bounds on the optimal rate. These bounds are then used to determine the optimal
rate for several classes of instances.
