Sadly the only relationship that truly and legally often ends is a marriage. Your parents, siblings, children, etc will always be your parents, siblings, children. But your wife/husband or spouse can get a divorce and never be your wife/husband or spouse again.
Legally it is the one relationship one can break away and walk away from.
Perhaps one way to stop that from happening is never to get into a such a relationship that has a way out. And the other way is to take the “I” and “Me” out of such a relationship and make it all our “YOU” or “US”. And honestly the second option sucks out your life. So it worth spending a lot of time and careful thinking before you invest is such a relationship.
We often offer such selflessness to our best friends, children and at times our parents and siblings. So why cant we do it for our spouse? Yes, provided they are the right one. And what does the “right one” mean to you?