Even if they have mentally and biologically defect offspring? Because you know that has a higher chance of happening with couples that are biologically related, and since Inori's a clone, I can only that chance being even higher.
Uhm... why should they necessarily have a child? Not every couple is going to have children. They could also adopt one. This has nothing to do with love. ^^" or else, people with AIDS shouldn't be allowed to love or have children too.