Marriage carries legal implications. Do you really want to sanction a 50 year old male being “married” to 72 13 year old girls? Or grandpa “marrying” he granddaughter? or grandsons?
The illegitimate action of the USSC has dissolved the meaning of the word “marriage” - it has no meaning. “Marriage” now includes any grouping of persons.
Some have proposed the idea of recognizing households, which would be far fairer in many ways. There would not even need to be sexual relations going on or implied for that.
Later