How/when to explain dad is not bio dad

Title says it all...how when should I explain this to my child who is 6. I don’t want to hide it, but I definitely don’t want to bring it up before he can truly understand what this means, and that the man who raised him loves him very much.I tried googling it, but I couldn’t really find specific advice... has anyone been through this? What were the results? Any help is appreciated. via /r/Parenting https://ift.tt/34Z9xhN