A QUESTION BEFORE I GO

A husband and wife were lucky to have four sons
The youngest boy was different to the older ones
The older three were tall had light skin, and red hair
While the youngest was short blue eyes and was fair
When the father took ill and was lying on his deathbed
With all his strength he turned to his wife and said
"Darling, before I die, please be totally honest with me
Is our youngest son mine as he’s not like the other three?"
"I swear on everything that's holy that he is your son."
The wife replied, and then with a smile he was gone
The wife then muttered to herself almost silently
"Thank God he didn't ask me about the other three."