Please do create a will or trust. Do it legally, get it notarized, find a lawyer if your assets are somewhat complicated (esp if you want there to be a his/her half split.) Do it for the family members you care about, if nothing else, EVEN if you don't leave them a dime. Here's why - if you set up nothing before you both pass away, the laws of your state will determine who inherits what. But what does that mean, in practice?
Will they appoint an executor from among your relatives? How will they determine who is most fit to serve? Will a state appointed executor act? How long will this executor, who doubtless is handling numerous other estates, take to do things like... sell property, liquidate accounts, obtain all your financial information? How will they even know where to look for all your financial information (and if you're taking the time to gather all this info up in one place for convenience sakes... you might as well make a will and trust stating how you want it passed on, LOL.) If your state laws say your estate will pass through probate, that means court - rounds of notices sent to every person who could conceivably be included in your estate. And if a single one of your family members decides to contest and kick up a stink about how receiving "their share" (and never underestimate what a desperate and greedy person will do), this could bog the whole process down for months if not years. If a responsible and caring family member steps up to take care of business and try to reduce the costs of administering the estate, they may have greedier and immature people on their backs kicking up a fuss if the work (and it is WORK) isn't done fast enough, or they're not receiving money fast enough, etc.etc. I worked as an admin in an estate planning law firm for many years, and have seen LOTS of family spats and disputes over "what grandma would have wanted" when grandma didn't set up a trust.
Not making your wishes clear means that the state and your family and loved ones will have to muddle along blindly without a roadmap, and people acting in bad faith will be able to make their lives much harder in the hopes of profiting from your money. Set up a will or trust -- you can always change it later, as your lives and peoples' circumstances change.