Just going to emphasize some good points made earlier:
1. Children are human beings, not pawns. Using them as such is selfish and irresponsible.
2. Babies strain relationships. They never bring a couple closer together unless the couple has full-time nannies, allowing them to parent by proxy.
If you want to strengthen your bond, plan activities together, have intimate conversations, plan the future.
Heck, if you want to go this route, why not have a big 4-some whenever the women are ovulating, kind of like russian-roulette pregnancy? Then the kids can just grow up never knowing who their biological father is, but all the 4 parents can raise all the kids as their own. Oh right, because that's a really stupid idea.
“As I am sure any cat owner will be able to tell you,
someone else putting you in a box is entirely different
from getting into a box yourself.” —bisexualbaker