Anyone who has been married previously and is seeking marriage in the Catholic Church should inform themselves about annulment requirements. (Remember that an annulment in the Catholic Church does not mean that there was nothing sacred in a previous marriage nor does it have any bearing on the legitimacy of children—this is a civil matter, not a Church matter). The Archdiocese of Boston addresses many common questions about the process in this FAQ, and offers more details here.
To learn more about annulments from one of our staff, please contact Fr. Rich Andre, CSP or Fr. Ed Nowak, CSP.