For freedom from fear you can use the runes Ansuz, Uruz or Munka.
You can meditate on the virtue "Death" to be able to better understand the phenomenon of death. Also, you can ask for help in familiarizing yourself with the subject of death with Lord Anubis.
Loss is inevitable. You can only make the most of the time you have with them now, so when they leave you, you are left with gratitude instead of regret.
Learn to have control over your mind. Having this constant fear doesn't help you in any way. One way to solve this is to focus on the opposite scenario of what you fear. Each time you have worries about this, think of your family members being full of health and safe.
If you want you can also protect them spiritually here and there. They will benefit.