Because my wife (cisgender female) and I (pre-op transman) are not yet legally married, we have taken what steps we can to protect ourselves if something were to happen to either of us. We have both had our wills drawn up and finalised, named one another as power of attorney and named one another in our Enduring Powers of Guardianship, which gives us the authority to make medically-relevant decisions on the other's behalf if either were incapacitated. This is in South Australia, so I don't know what options are available to couples elsewhere.