This is so co-dependent. Why would anyone want to entangle themselves with multiple partners? God has ordained marriage between one man and one woman, and this design is foundational, just like the 7 day week. Every time you try to change these standards, all hell breaks loose. If you are having problems in your marriage or raising kids, get help through counseling. Don't go outside the marriage and involve other people in your mess. And visa versa. Its just common sense.