As others have said, there is nothing wrong and no problem to solve.
With regards to your son, I wish you all the luck in the world. I also have a 5 you little boy who is very attached to his daddy. He does not know, yet, and I am afraid that he will not take it well (at first). But remember, kids are (at heart) very accepting… discrimination and hate are learned traits not innate traits. Find a good child therapist (who has experience in this area) to help and give him some time/space.. I suspect that he will come around.