I have a colleague who has just secured a new job. Part of his responsibility is to manage his own bosses directs. Essentially these are his peers but he is in a more senior role. His boss is a high D and very controlling. How should he approach the relationship with his 'peers' ie he is expected to treat them as his directs but they still technically report to his manager. 

The company has clear retention problems and part of his brief is to try improve this situation. Advice and comments would be welcome.