Dear Liza: I set up a living trust and back up will naming my 3 minor children as beneficiaries.  What if one day, me, my husband and all children die at the same time in an accident? 
Both my parents and in-laws do not live in US.  If none of me, my husband and children survives, I want our estate to pass to our families in Asia.  What is the best way to set this up in my will and living trust? Here’s what you do: put in a section that says that if you, your husband, and all of your children (and their issue–your grandchildren, great grandchildren, and so on…) don’t survive you, that you want your estate split equally between your husband’s surviving parents and siblings and your surviving parents and siblings. I call this the “God Forbid Clause” since it covers an unexpected, but not impossible, scenario.  You can leave your estate to anyone you choose to of course–family, friends, charities.  The important thing is to be specific if you have specific people that you want to benefit. If you don’t really know who to leave your assets to at this point, you  could be more lawyerly and less specific and say “your legal heirs” and this would then be determined under the laws of the state in which you executed your estate planning documents.  If you name specific people you would say where they presently live. And you would let your Trustee and Executor know how to find them by giving them a list of where your parents/siblings live and how to reach them. If your family lives abroad, the tax treatment of their inheritance will depend upon the laws in that jurisdiction.