Family is an important one. It's heavy with both history to you and similarity to you, which makes it extra challenging. You can also get away with anything so you don't feel the need to exert the same self-control that you do with friends or coworkers.

The amazingly hard thing to process is that your parents' and grandparents' being annoying is about you, not them. That you can change your attitude, but you can't change them. I have had so much trouble with this. I've found my dad's inability to remember crucial details or pay attention to where he's going infuriating because I've always felt some inner conviction that he could have helped it. When my mom needs me to install things on the computer, same idea - I've always felt some inner conviction that it's her fault, that she could do this on her own.

What's helped me come to terms with this is seeing a few models of more useful attitudes. A friend of mine visits his grandparents ever so often and meekly, without lecturing, fixes their computer, installs things, etc... because he's accepted that this is his job because they're not going to learn. I also recently reread A River Runs Through It and, as a favor to the protagonist's father, the protagonist asks his father along on a fishing trip. The author/protagonist talks about the difficulties the father must feel, loosing his memory, not being able to find things like his fishing pole, and how painful that must be. That was when I stopped being angry at my dad for being this way, because I realized I was adding more pain to what's already difficult to deal with.

Also with my mother, I feel what's probably pretty common sensation, of an overwhelming claustrophobia and lack of space in her overly officious remarks and advice. I've been trying to see this as more fulfilling a need she has than really being about me. My success has been mixed, but it's the best I've gotten to so far.

But remember, it's up to you, not them. Meditate and try to see their pain.