As obviously stated by the summary and the tags, this is a BL story. I would like to reiterate for the individuals in the back once more, this is a BOY x BOY LOVE story. Only, let's add a little twist.
This story is male pregnancy, meaning that it is possible for cis-gender men to get pregnant. In this universe it is possible because of a mutation that takes place in utero. This causes the men to have outer male reproductive organs but internal female reproductive organs. Men can only be diagnosed with this mutated gene at birth.
Don't think about it too much, honestly just go with the flow.