I stupidly have asked that question before. it is useless because you either know the person is lying or it is an answer you didn't want to know. I know because I have been asked and have smudged my answers by a few. Anyway, I think the important thing to remember is that they left their other partners (hopefully) and are now with you, and keep in mind that while they were with someone else that you were probably also with someone else. In my opinion as long as they are disease free, provide for prior children,if any, and treat you good....what does it matter.