A,B,C, and D are related to each other.
It is known that:

1. One of the four is the opposite sex from each of the other three.
2. D is A's brother or only daughter.
3. A or B is C's only son.
4. B or C is D's sister.

Determine the sex of each of A,B,C, and D. What is the relationship between these four individuals.

Note: For the purposes of the problem:

• There are no additional sexes other than Male and Female.
• There are no marrying siblings or plural marriages.