Throughout the US, a divorce can be obtained only through an order of a court of competent jurisdiction.
No matter how long the spouses have been separated, if they have not been divorced by a court, they are still legally married.
Depending on the laws of the relevant states, if the spouses have been living separate lives, they many have little or no right to the properties acquired during the separation.
The spouses likely should review their facts and options with an attorney.