I divorced my wife three times and her mother knows that. She [divorced wife] has two elder sisters, one of whom is married, and both of them know about the matter of divorce, but the men in the family do not know. Last week, this woman and her mother asked me to be the guardian in marrying the middle sister, and indeed I was the guardian and I lied and mentioned that I was the husband of her little sister, and the marriage contract was concluded. The question is: does my lying invalidate the marriage despite the fast that the bride and her mother know about the matter?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.

If you were appointed as a guardian with the consent of the guardian of the girl whose marriage contract was concluded, then the marriage is correct. Your statement that you are the husband of her little sister does not affect the validity of the marriage contract, as one might understand that this relates to the past. Anyway, this is a lie and you must repent for doing so, but this does not affect the validity of marriage as we mentioned.  

Allaah Knows best.