jlb684: Different cultures from mine do allow this, as I'm sure you know. You ask if it's ok...that is up to you, your wife/wives, and your religion to decide. I don't think it's right or a good thing, but I am saying this from the standpoint of my own culture and what would or would not suit me.
If you are asking if it's ok to have 2 wives secretly, I don't think any religion or culture would condone that...it's deceitful.
Sure i know in EU we can not keep more then one wives at one time but as your defination about different cultures world is quite big and different cultures are many