Based on this xsibase thread, here’s a little video that shows how to make the particles in one cloud act like the children of a particle in another point cloud. Basically, the idea is to have the same behavior as objects in a hierarchy, where the children “inherit” the transformations of the parent.

One thing I forgot to mention in the video is that because both point clouds are at the origin, I don’t have to worry about converting between two different local coordinate systems (aka reference frames).

Example scene here.