A dream about an in-law represents scrutiny and insecurity in regards to new responsibilities. You may have recently experienced a promotion but be having conflict with your boss. This person has strong influence upon your life and you may feel the problems someone is causing you for an unexpected downside of a greater reward.
Alternatively, to dream of your in-law symbolizes an evolving working relationship. The dream may also be a hint to strictly adhere to the rules and be mindful of your actions.