This is an increasingly common situation. The best solution is to use trusts, either a joint one created by you and your significant other or separate ones that you each create. In either case, you can provide that the house will be held in trust for the survivor and then the proceeds ultimately distributed as you direct.
There are a few issues you will need to discuss: Who should serve as trustee? Who should have the right to appoint and remove trustees? What happens if the survivor no longer wants to live in the house, can’t afford to maintain it, or can no longer live independently? Who would get to decide to sell the house? What would happen to the proceeds? The more answers you work out in advance, the better things will function in the future.
We recommend you consult with an elder law attorney in your state. Find one near you.
For more information on planning for the nontraditional family, check out this article.