One doctor told me that some couples have a mismatch of their genes that even if the husband and wife are found to be both fertile, they still couldn't conceive. That is the X factor in pregnancy that the egg cell should also be compatible with the sperm cell. It may not have a conclusive proof but I tend to believe because I know of not just several but many couples who are childless.
I thought that this was a myth or something. To be honest it is pretty hard to accept these kinds of conclusions.
Is that the case? I never heard of that yet. However, here are the other causes of infertility: https://my.clevelandclinic.org/health/diseases/16083-infertility-causes
This is the first time I am hearing about such a scenario. Probably this explains why there are some couples who are unable to conceive no matter how hard they try, in spite of having perfectly good physical health as well as having no issues with respect to their sexual health and organs. I wonder how this can be avoided, perhaps a pre-marital screening? But how would it help if the couples are really in love with each other and want to have kids of their own?
Have kids before getting married, that should work. I bet this will save you a lot of heartache when you find out you are a mismatch.