Age limits apply to many trip cancellation policies in terms of the illness or death of a relative. The age your relative can be will vary with insurers, but many set a maximum age of around 90, after which the illness or death is not deemed to be 'unexpected' and no cover is offered. Some travel insurance brands do not state an age limit, but the health of your relative is a condition many policies will consider.
If your relative is elderly and you are concerned about whether you will be covered if an incident occurs while you're away, you should read your product disclosure statement (PDS) carefully and contact your insurer for further information.