It is strange, I agree. We can also say the sons are so hopped upon mood altering drugs to dull the pain, they're lead around like dogs on a leash.
I don't know the sons, although I'd assume they followed their parents politically, but their coolness over their deaths is hard to explain.
That's why I think they're still in shock. They don't know what they're doing right now. I have to give them the benifit of the doubt. Like I said, I've never met them.