From the given information, we can determine the relationships within the family as follows:
A and D are brothers.
A is a doctor.
E is married to one of the brothers (either A or D).
E and the brother she is married to have two children.
B is married to D.
G is the child of B and D.
Since A is a doctor and is a brother of D, and B is married to D, we can conclude that B is married to A. Therefore, E is married to D, and they have two children. This means C is one of the children of E and D.
Thus, C is A`s son.