Logic Puzzle

I need to think through this step-by-step.

Given information:

• Sally is a girl
• Sally has 3 brothers
• Each brother has 2 sisters

Let me work out how many sisters are in the family total.

If each of Sally's 3 brothers has 2 sisters, and all the brothers are in the same family, then there must be 2 sisters total in the family.

Since Sally is one of those sisters, and there are 2 sisters total, Sally must have 1 sister.

Therefore, Sally has 1 sister.