One of the disadvantages of being "older" parents is we have a lot of extended family members who are old. Not in the "getting old" range, but in the 80+ years old category. No matter how you look at it, 80+ is considered old.
In the past few months, the girls lost two "Grammas." One was an uncle's 95-year-old Mom who became an honorary Gramma to the girls. She adored them like her own. This past weekend, they lost my 93-year-old Grandmother, who the girls called "Great Gram."
Our conversations about death have been general as they are only five years old. When we first tell them, they ask the usual questions about what happened, how a person dies, etc. We talk a lot about how when a person dies their heart stops, they stop breathing, etc. We never use the "they went to sleep" line. I've read enough about how that frightens the children and they really don't want to go to sleep. The blond twin can barely sleep after watching a Disney movie. Can you imagine what would happen if we told her that dying is like going to sleep?
The brunette twin talks about us dying. She wants to know when we'll die and who will take care of her then. She wants to know if it will hurt and why people die at all. She's quite practical in her approach to the topic.
The questions that follow, hours or days later, are pretty funny -- if you can call any question about death funny. Yesterday we were driving when the blond twin said, "Can we turn off the music and talk about the death thing again? Tell us again how Great-Gramma died." And, so, we did. We talked about how Great-Gramma died and what it means to die. Both twins asked a few questions and then changed the topic.
This is how it will go for a while. They ask questions as they think of them. We answer them in the most age-appropriate manner we can come up with at that moment. It's not a perfect system, but it's the best we have right now.