Complaint Review: Aon Travel insurance/ Royal Caribbean

We bought our parents a cruise for Christmas and bought the travel insurance since they are in their 70's and who at that age doesn't have something they are seeing a physician for.  We gave it to them at Christmas and they told us my dad had to have Cariac Ablation surgery done the same week the cruise was booked for.  They called to reschedule it and were told to cancel the first cruise and just rebook for a later date.  They did, and were told to have all this paperwork filled out by their doctor.  After mutliple and frustrating calls and trips to the doctor to have them fill our more and more paperwork they recieved a letter that their claim was denied for pre-existing conditions.  Now a gift that was given has been nothing but a nightmare.  I would and will never buy travel insurance again because they will find something in your medical history as pre-existing conditions and deny your claim  Not to mention we were the ones to purchase it and had no idea about this procedure and current health problems.