It depends how old the previous petition is. If it was issued, say, five years ago you could certainly apply to have it dismissed. On the other hand if it is quite recent you would first have to write to your ex and invite him to dismiss it by consent (keeping a record of the correspondence). Assuming he did not co-operate and/or reply you could rely upon the correspondence to show that you had made every reasonable attempt to deal with it by agreement before making an application to dismiss.
