Mr. Burton has a wife and a daughter; the daughter has a husband and a son. The following facts refer to the people mentioned:

1. One of the five people is a doctor and one of the other four is the doctor’s patient.
2. The doctor’s first offspring and the patient’s older parent are of the same sex.
3. The doctor’s first offspring is:
• not the patient, and:
• not the patient’s older parent.

Who is the doctor?