Each new person you add to the polycule brings exponiential relationships.

Traditional monogamy gives you one relationship.

Add in another person and you have two...

Nope!

Let's say you have a husband and a wife.

You have to worry about:

1. Your relationship with your husband.

2. Your relationship with your wife.

3. Your husband's relationship with your wife (even if they are not also married to each other).

4. The relationship of the entire group.

So you add one more person and you add TWO more relationships. So, you have three wives...

1. Your relationship with wife 1.

2. Your relationship with wife 2.

3. Your relationship with wife 3.

4. Wife 1's relationship with wife 2.

5. Wife 2's relationship with wife 3.

6. Wife 1's relationship with wife 3.

7. Everyone's relationship together...except that you have so many...

And that's why if you want to PARTNER with your multiple partners, you either have to put in a lot of work or limit the number. (It's probably why Mohamed told guys not to have more than three wives too. Ahem).

Which is why a lot of polyamory is hierarchical. You have your nesting partner with whom you do all those things, and then secondary partners.

Not everyone can have more than one primary partner (and many people who can don't because they can't find a compatible person who can...)