You can use your will, trusts, will substitutes, and other estate planning tools to take care of everyone you are even remotely related to, including your 19th cousin, twice-removed who lives in Latvia (and whom you have never met in person). As a practical matter, however, you probably want to concentrate your efforts on your closest relatives: your children, grandchildren, siblings, and (if they're still alive) parents and grandparents.

However, you still need to make some key decisions about your closest relatives regarding your estate plan. For example, you may want to simply leave all your estate to your children, who in turn will someday leave that property (or, more accurately, whatever is left) to their own children. Conversely, if your children are particularly well off, you may want to leave the majority of your estate directly to your grandchildren (perhaps in trust). Or you may have a favorite cousin who has always been like a sister to you, and you want to help her out, perhaps even ahead of your own children and grandchildren.