My two are biracial, white and Latina, and I do get this question quite often. I never take offense though. The oldest is 4 and looks completely mexican, just like her father, and my youngest is 9 months and looks like a Latina version of me. I just think people are curious to see if they are mine or are adopted, and let them know politely that I did, in fact, give birth to them. I live in Vermont, so there's not a huge amount of diversity here, so our children appear very exotic for the area.