I was probably 36 years old before I witnessed a truly healthy, largely-undysfunctional family. The one difference I noticed between this family and all the rest I had known in my life is that the father was a good, moral, and strong person who had established very healthy parent-child relationships with his sons. I also noticed he served as a mentor and friend to the boys, but did not expect them to be his friend (related to supporting, advising, or sharing his adult issues).
I agree with sojourner how these roles do exist in all families and I'd like to add that in healthier families, the roles are not as strong as in unhealthy families. Meaning, the child doesn't get forced into a role, or otherwise pegged as one thing or another day after day; and there's no drama, yelling, and blaming of the child for one little thing he does or says.