If your question is how to write about someone’s ex-wife, ex-husband, or former spouse in an obituary, here are some guidelines.
If the deceased person has remarried, list the current spouse’s name first in the survivors, followed by the children and parents of the deceased person. If you wish to list former spouses with the other survivors (and this is totally up to the family to decide), these names should be listed after the immediate family members.
If your question is how to write an obituary for someone who has two or more wives or husbands at the same time, then you can simply include all of them in the list of survivors. You might want to list them alphabetically, by marriage date, or in whatever order makes the most sense to your family.