Good point. As others have noted, the use of "than" might not be a problem at all. But the issue you bring up certainly is. EDIT. If you look carefully, you ca

Good point. As others have noted, the use of "than" might not be a problem at all. But the issue you bring up certainly is. EDIT. If you look carefully, you can see that the sentence is not actually ambiguous. The word "which" is followed by a singular verb: "has". So the antecedent cannot be "families" or "mothers", which are plural; it must be the clause: "... being raised ....". However, I still agree that the sentence should be restated. Making people think hard to figure out the antecedent of a pronoun, is hardly the way to communicate effectively.