GMAT Data Sufficiency (DS) | Re: If Ms. Anna and Mr. Mathew are children of Mrs. Smith, how many brothe

From Statement (1) alone, we have that Ms. Anna has the same number of brothers as sisters. If m is the number of male children Mrs. Smith has (so Anna has this many brothers), then she must have m sisters also. Hence, including Ms. Anna, Mrs. Smith must have m + 1 female children. Now, the number of children Mrs. Smith has equals m + (m + 1) = 2m + 1. But, we still do not know the value of m. Hence, Statement (1) alone is not sufficient.
From Statement (2) alone, we have that Mr. Mathew has twice
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