Ian McShane and Robert Shaw - Relationship?

I just watched this on DVD. It has been a long time since I've seen it.

One thing I have never been able to figure out. What is the relationship between Robert Shaw (Squadron Leader "Skipper") and Ian McShane (Sgt. Pilot "Andy").

Are they brothers, Father/son, Father-in-law/Son-in-law or just Squadron leader/subordinate?

When Andy shows up at the hangar after being shot down, Skipper chastises him for being stupid then asks "You call your wife?" and when Andy answers he says "Cut out the sir." he then head nods to the car and says "Get in Boy."

After Andy's wife and sons are killed, he is shown as having spent the night at Skippers house.

I get the impression there is some kind of family connection between the characters but nothing is ever really said.

Guess she didn't like the cornbread either.