As a dutiful son I carried out her last wishes, to the letter.
Being the dutiful son, he listened and left it alone.
He looked after his father, like a dutiful son should.
"But she can't stop me from being a dutiful son!"
"My feelings toward you are those of a loving and dutiful son."
He was, apparently, a dutiful son and the mother a source of much distress to him.
He would go with his father, yes, and present the appearance of a dutiful son.
In my country, a dutiful son is expected to take care of his parents when they are old.
"I was a very dutiful and good son," he said.
The dutiful son increased his visits to three a year.