As you grow older or as your parents grow elder, the need to be proactive with your planning becomes all the more important. At the very minimum, this means providing a trusted individual with your power of attorney. A more comprehensive estate plan will, of course, have many more elements in place, but this is a good starting position. 
Not having a power of attorney can present legal problems if someone does need assistance with making decision. If there are behavioral issues with an elderly individual, a conservatorship proceeding will happen, likely meaning that all relevant parties come with their own legal representation. This can be very expensive for everyone involved.
If the issues are medical as opposed to behavioral, without a power of attorney family members are looking at a guardianship proceeding. This involves situations in which a loved one or friend attempts to convince the court that a guardian is indeed necessary and that he or she is the best person for the job.
If you would like to plan ahead so that your family members are not facing this difficult task alone, contact an experienced elder law attorney for more information.