I am sorry to hear this too. As Wingy said, divorce is never easy for all involved. I don't have experience with this exactly, but when my son (and one of Timber's favorites) went away to college it didn't seem to have a big effect on Timber. When Dakota comes home, Timber acts just like he always did toward him. I'm sure he wondered where Dakota was, but it didn't affect his health or behavior. Good luck!