Riddle - Parents, children and eggs

Two parents and two children sat down to eat eggs for breakfast. Each ate an egg. How many eggs did they eat in total?

to 1
b) 3
c) 5
d) 8


As the answer must be among the alternatives presented, we conclude that the right answer is 3 eggs. How does this explain? One of the parents was also a grandfather. Therefore the other father was both father and son, resulting in a total of 3 people.