A domestic partnership is a legal relationship between two individuals who live together and share a common domestic life, but are not married (to each other or to anyone else). Some legislatures have voluntarily established domestic partnership relations by statute instead of being ordered to do so by a court.
Is it illegal to be in a relationship with more than one person?
Polyamory should not be confused with bigamy or polygamy, which involves marriage to more than one person and is illegal in the United States. Consensual nonmonogamy is an umbrella term that psychologists use to describe swinging, open relationships, and polyamory.
Do life partners have legal rights?
Generally speaking, your partner has no legal say in your medical treatment if you end up in a situation when you cannot make decisions yourself. If you want to give the person that right, you can give them a durable power of attorney over health care.