This is a bit of a word puzzle! Here's how to solve it: Sally's brothers all share the same sisters. They aren't each talking about a different set of sisters.

This is a bit of a word puzzle! Here's how to solve it: Sally's brothers all share the same sisters. They aren't each talking about a different set of sisters. Sally is one of those sisters! Each of her brothers has Sally as a sister. Since there are 2 sisters total (Sally and one other), Sally has one sister. Let me know if you'd like to try another brain teaser!