Was my grandfather in the wrong??

My grandfather recently passed away from multiple health issues, and was in and out of the hospital for the past year and even more so during his last few months before death. My mother and I have been the main caregivers throughout all of this, but my mother ended up getting a job as a travelling surgery RN in September 2012 and I have been taking care of my grandparents since. Long story short, my grandfather and grandmother basically raised me since my mother was a single parent and they are more than just grandparents and I would do anything for them and have not regretted being their caregiver one bit, but my mother's one brother, however feels different. I have two uncles, one who I will call "Key", who is the oldest, and "Miller" who is the middle child. Both Key and Miller have well to do jobs and both are very busy. However, Key has made more of an effort of trying to help out and things I am not able to do (fix cars, mow the lawn, clean gutters, plumbing issues, etc) while Miller has not been around. So when my grandfather was admitted to an long term care facility for bounce back rehab, we had POA papers drawn up. During his last weeks, Pop was very tired and sometimes unresponsive, but was still sharp as a tack and his primary care doc deemed him mentally competent to still make his own decisions. Pop named Key, my grandmother, and I POAs and three days after the papers were signed, he passed away while getting ready for discharge. Miller found out, as well as other several family members, all of whom were utterly angry that Miller was not a POA. They have made me feel guilty and horrible... but was my grandfather really in the wrong by not putting Miller on there? Miller was never there... had no clue half of the time what was going on with their medications or medical issues, and only really showed up when Pop was in the hospital. I never wanted to be POA, but that's what Pop wanted. But was he in the wrong for picking the grandchild (me) over his one son??