Thanks for the question.
It is likely that his former marriage would be considered invalid since he was married outside the Church. In that context, he would need a dispensation from the canonical form to have a valid marriage, and without it is, defacto, null. That is irrespective of her prior marriage, which also would have made it problematic.
I would suggest talking to a priest should the relationship get serious, but I don't think you have a problem with annulments.