A family consists of six members P, Q, R, X, Y and Z. Q is the son of R but R is not the mother of Q. P and R are a married couple. Y is the brother of R. X is the daughter of P. Z is the brother of P. How many children does P have?

Introduction / Context:
This family puzzle asks for the number of children of one member, P, using a mixture of marriage relations, parent child relations and sibling relations. It is similar to many reasoning questions where you have to untangle genders and family roles from a short text.

Given Data / Assumptions:

• Members: P, Q, R, X, Y, Z.
• Q is the son of R, but R is not the mother of Q, so R is the father.
• P and R are a married couple, so P is the wife and R is the husband.
• Y is the brother of R, so Y is male in the same generation as R.
• X is the daughter of P, so X is a female child of P.
• Z is the brother of P, so Z is male in the same generation as P.
• We assume that Q, as the son of R, is also the child of P, since P and R are married.

Concept / Approach:
The key idea is to classify everyone by generation. P and R form the parent couple. Their siblings Y and Z are in the same generation. The children generation consists of the sons and daughters of P and R, which must include Q and X. Once we know this, the direct count of P children becomes easy.

Step-by-Step Solution:
Step 1: From "Q is the son of R but R is not the mother of Q", we know R is male and is the father of Q.Step 2: "P and R are a married couple" tells us that P is the spouse of R. Therefore P is the mother in this family pair.Step 3: If Q is the son of R and R is married to P, it is natural and standard in such questions to treat Q as a child of both P and R, unless told otherwise.Step 4: "X is the daughter of P" adds another child directly linked to P. Since P and R are married, X is also the daughter of R.Step 5: So far, P has two clearly stated children: Q (son) and X (daughter).Step 6: Y, the brother of R, and Z, the brother of P, are in the same generation as P and R and are not children of P. Therefore they do not change the count of P children.Step 7: Hence, P has exactly two children, Q and X.

Verification / Alternative check:
Draw a quick tree. Place P and R as a married couple in the middle. Draw X below them as daughter of P. Draw Q below them as son of R, and by marriage assumption also son of P. Place Y next to R as his brother and Z next to P as her brother. Now the only members below P in the tree are Q and X, confirming that P has two children.

Why Other Options Are Wrong:
A count of 1 child would mean either Q or X is not considered a child of P, which contradicts the direct statement and the married couple assumption. Counts of 3 or 4 would require treating Y or Z as children of P, but both are described as siblings, not children. A count of 0 is impossible because X is explicitly called the daughter of P.

Common Pitfalls:
One frequent mistake is to ignore the phrase "P and R are a married couple" and treat Q only as the child of R, not of P. Another is to get confused by the presence of brothers Y and Z and accidentally count them as children. Keeping a clear separation between generations and labelling each person on a simple diagram prevents these errors.

Final Answer:
P has 2 children in this family.