One of Mr. Bajaj, his wife, their son and Mr. Bajaj’s mother is an Engineer and another is a Doctor.
- If the Doctor is a male, then the Engineer is a male.
- If the Engineer is younger than the Doctor, then the Engineer and the Doctor are not blood relatives.
- If the Engineer is a female, then she and the Doctor are blood relatives.
Mr. Bajaj's wife and mother are not blood relatives. So from 3, if the Engineer is a female, the Doctor is a male. But from 1, if the Doctor is a male, then the Engineer is a male. Thus, there is a contradiction, if the Engineer is a female. Hence, either Mr. Bajaj or his son is the Engineer.
Mr. Bajaj's son is the youngest of all four and is blood relative of each of them. So from 2, Mr. Bajaj's son is not the Engineer. Hence, Mr. Bajaj is the Engineer.
Now from 2, Mr. Bajaj's mother cannot be the Doctor. So the Doctor is either his wife or his son . It is not possible to determine anything further.