What a strang couple,do you know what they might be?

Tweet

After entering the restaurant,my friend and i were very expected today`s dinner--grilled fish.It is the most famous grilled fish in our city.Sitting down with a great pleasure,i found sth strange beside our site.A middle-aged man and a boy seemed 17 years old were sitting beside us.The boy did not say anything and even ate a little,yet the man seemed a bit hungry,ate the grilled fish lonely just like there was nobody here.It puzzled me a moment then our food was already brought in. Though the food was so delicious,i always thought about the two people.Why did not say anything,what`s their relationship finally? When the man called the waiter to add other food,the boy finally said sth.I could not hear clearly,but it sounds like "dad".That`s really surprised me,why their relationship seemed so embarrassing and uncomfortable. My guess is the middle-aged man maybe was the stepfather.Of course,the boy didn`t like him very much,and the man really wanted to close to him. Well,do you think about it?Have you even seen that before?