If the matter is as you mentioned, and that you married the young one after the old, you should renew the contract made for the young one after the expiry of the `Iddah (woman's prescribed waiting period after divorce or widowhood) of the older woman. This is because the first contract made for the younger one is not valid, as you married her (Part No. 18; Page No. 245) while you were still married to her maternal aunt.
Marrying a woman and her aunt at the same time is impermissible, as it is prohibited by the Shari`ah (Islamic Law). May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.