We have seen what happens when one or both spouses has outside their primary relationship. It rarely ends well.
I WAS UNDER THE IMPRESSION THAT V RELATIONSHIPS, OFTEN WITH ONE MARRIAGE, IS PRETTY STANDARD FOR SUCCESSFUL POLY RELATIONSHIPS. THE POLY PEOPLE I KNOW ALL DO VEES (OR MS OR WS).
ANOTHER THING ; WHEN I MET MY BOYFRIEND IT SOON BECAME CLEAR THAT MY HUSBAND WAS NO LONGER THE SOLE PRIMARY. I SHARE EVERYTHING EQUAL BETWEEN THEM. IT TOOK MY HUSBAND A WHILE TO ADJUST, BUT NOW HE SAYS IT IS ONLY NATURAL. IT IS LIKE WE HAVE ALWAYS DONE IT LIKE THIS. NOT EVERY RELATIONSHIP HAS JUST ONE PRIMARY.
The other danger is that your girlfriend is only with you for sex and fun. They are not on your back to do more around the house, go to the store, and do all the boring stuff that has to be done in a marriage. For this reason, they are more exciting and appealing than your wife who you just had an argument with.
I LIVE IN TWO PLACES, WITH TWO HOUSEHOLDS. I DO BORING AND EXITING STUFF WITH BOTH OF THEM.
I even left my wife once for a brief period of time because I loved my girlfriend so much.
WELL IF THERE EVER WAS A THING NOT POLY, THAT IS THE ONE.
Also beware that new love is always more exciting. Who does not get excited with a new sex partner? It is new and different...
THAT'S WHY WE CALL IT NEW RELATIONSHIP ENERGY.
It is a juggling act at times to make sure all parties feel equally loves and paid attention to.
AFTER THE FIRST YEAR, IT JUST GETS EASIER. THEY ARE NOT JEALUS NOR VERY INCLINED TO FEEL NEGLECTED. PERHAPS GUYS ARE EASIER?
...As much as some want to think that poly is the way to go, evolution conspires to keep a couple together using jealousy and emotional bonding. If those two things did not work well to pass on our genes, we would not be here.
AS MUCH AS SOME WANT US TO THINK MONO IS THE WAY TO GO, RAISING KIDS IN LARGER GROUPS HAS BEEN THE STANDARD, FOCUS ON THE COUPLE IS A NEW THING IN CHILD RAISING HISTORY. MEN HAS THROUGHOUT HISTORY ALWAYS BEEN ABLE TO HAVE MULTIPLE LOVERS AND BEGET CHILDREN BY THEM. SOME RARE PARTS OF THE WORLD, THAT HAS BEEN THE RULE FOR WOMEN TOO. AT THE SAME TIME, PEOPLE ARE WIRED FOR WANTING TO FEEL SPECIAL AND PERHAPS EXCLUSIVE, AND MONOGAMY HAS BEEN POPULAR, TOO. THE HUMAN EXISTANCE IS MANYFOLD. WE SHOULD BE WEARY TO USE NATURE TO EXPLAIN AND JUSTIFY OUR OWN RELATIONSHIP PREPERANCE. VERY RARELY HAS PEOPLE BEEN ABLE TO CHOOSE FREELY BETWEEN MONO, POLY AND ALL THE REST, THE ONLY WAY OF KNOWING WHAT REALLY WORKS IS TO CREATE REAL OPTIONS.