Exclusively refers to a couple's initial marriage, probably at age 24 or less, involving partners with little income and assets. May or may not end with children; will likely not end with more assets than when it began. One or more of the partners may have an advanced degree at the time of divorce. Subsequent marriages are usually to partners higher up the socio-economic scale.
All she got was a '84 Suburu and some crummy dishes. No jewels, no real estate, nothing really to split; it was a starter marriage.