Are you sure Kaiser behaves that way because he is too attached? I ask because Benny is the same way with Jake our Borzoi, but is it because Benny is the alpha of the two and seems to feel responsible for Jake.
When DH and I walk the dogs together, Benny does not want Jake to take the lead when out walking and when Benny is in the leas he will check back and want to wait if Jake gets to far behind.
If we are in an off leash area and Jake wanders off Benny will herd him back. He does not like even our human family members to wander off and seems to feel it is his responsibility to keep the pack together.
I think the LAT game or some focus work could help with Kaiser. Maybe just start with letting Pookie only a little ahead and then increase the distance