No – it applies to all Immediate Family Members, travel companions and their Immediate Family Members- whether they are traveling or not. This is an important detail to pay attention to because most travelers think that the pre-existing condition exclusion only applies to them – the ones going on the trip. If you are concerned about a parent or other close relative who is back home and not traveling its best to try to get a plan that will waive the pre-existing condition exclusion. The plans that offer this waiver do not charge more for it – it is a time sensitive benefit that you qualify for by purchasing the travel insurance plan close to (within anywhere from 7-21 days) your first trip payment(also refered to as Initial Trip Deposit). A couple plans also offer it if the insurance is purchased before or within 24 hours of your Final Trip Payment.
I would dare say that a majority of denied claims can be traced to this exclusion – most people do not talk about their medical problems with other people, even other family members. To find out that the reason you cancelled your trip was due to a family member’s pre-existing condition when a claim is denied is not a good time. Its best to be safe and get the insurance early and get the wavier.