Ad Orientem, I’m not 100% sure that analogy is as helpful as it could be.
I’d go more like this: Male-female complementarity (wow. Actually spelled that keyboard breaker!) can be seen in much the same vein as an electric plug and socket. When you insert a plug into the wall socket, you get electricity. Trying to hook up an extension-cord socket to the wall socket or trying to mate two plugs is an exercise doomed to failure… not only will you get no electricity, but you have to use extraordinary means to keep the two even together. In that case, they’re being used in a way that is completely unintended by the maker of either the appliance or the wall socket, to the futility (and possibly detriment) of both.
The sterile partner in a heterosexual marriage would be like a socket or plug that is defective. It may not, at this time, carry electricity through to the appliance, but there is nothing that says that is 100% permanent (just as a socket can possibly be repaired, there are new treatments that could be both licit and effective in restoring the partner’s fertility.) They’re still doing what they were designed for, it’s just that something went wrong in one or the other of them.
Does this help, OP?