|A) If the data in statement I alone are sufficient to answer the question
|B) If the data in statement II alone are sufficient answer the question
|C) If the data either in I or II alone are sufficient to answer the question;
|D) If the data even in both the statements together are not sufficient to answer the question
From statements I and II together, we can conclude only that either B is the sister or brother of A.
So, even from both the statements, the exact relation cannot be known.