In a family, there are six members A, B, C, D, E and F. A and B are a married couple, A being the male member. D is the only son of C, who is the brother of A. E is the sister of D. B is the daughter-in-law of F, whose husband has died. How many male members are there in the family?

Introduction / Context:
This is a family puzzle that asks you to determine the number of male members based on a short description. It combines information about marriage, parent child relations and gender words like brother, son, sister, husband and daughter-in-law. These clues must be joined logically to identify who is male and who is female.

Given Data / Assumptions:

• Family members: A, B, C, D, E, F.
• A and B are a married couple, and A is male.
• C is the brother of A.
• D is the only son of C.
• E is the sister of D.
• B is the daughter-in-law of F.
• F husband has died, so F is a widow and therefore female.
• All six mentioned persons are the only members we count.

Concept / Approach:
The technique is to mark each person as male or female based on the strongest clue associated with them. Words like brother, son, husband clearly indicate male, while sister, daughter-in-law and widow clearly indicate female. Once every member is classified, we simply count the males.

Step-by-Step Solution:
Step 1: From "A and B are a married couple, A being the male member", we mark A as male and B as female.Step 2: "C is the brother of A" tells us that C is male.Step 3: "D is the only son of C" tells us D is male and a child of C.Step 4: "E is the sister of D" tells us E is female and a child in the same generation as D.Step 5: "B is the daughter-in-law of F, whose husband has died" implies that F is a female elder relative (the mother-in-law). Her husband was another male, but he is not one of the six listed members, so he is not counted.Step 6: Now classify: A (male), B (female), C (male), D (male), E (female), F (female).Step 7: Count the males: A, C and D. This gives exactly three male members in the family.

Verification / Alternative check:
It is useful to draw a quick family sketch. Place F at the top as an older female whose husband is deceased. She has a son A, who is married to B. C is stated to be the brother of A, so he is another son of F. C has children D (son) and E (daughter). This picture confirms that there are three males (A, C, D) and three females (B, E, F) among the six named members.

Why Other Options Are Wrong:
A count of 1 or 2 males would mean that either C or D would have to be female, which directly contradicts the terms brother and son. A count of 4 or 5 males would force us to treat one or more clearly female roles such as sister, daughter-in-law or widow as male, which also contradicts the description. Therefore only the count of 3 is consistent with all the given clues.

Common Pitfalls:
A typical mistake is to accidentally include the dead husband of F in the head count, even though he is not one of the six listed members. Another error is to misread the phrase "only son of C" and think it changes the number of males directly, when it only clarifies that D is male and C has no other sons. Always restrict counting to the named persons and use gender words carefully.

Final Answer:
The family contains 3 male members.