The first thing I would do is set appropriate limits and boundaries with him by disciplining the behavior. Secondly, I would think that it would be a good idea to at least consult with a mental health professional seeing that this behavior re-occurs especially with a stranger. This could be a sign that he was sexually abused. You definitely want to get a handle on this situation now while he is young.
This is an abnormal behavior of a child in his age ,.He is not born knowing about sex and how it is done ,.it's an ccquired behavior . He don't know anything about sexual relations . Only he do what he see . This is like he say what he hears , he will not say any word that is not heared before .
Now , you should keep an eye on your child , what he see on TV , internet .or even you and your father , his relatives ,.
Your child need support from you . Never spank or shout to him , bcoz it will come back with anegative impact on him.
Hope everything will be fine .
Thank you,since leaving this post he is now seeing a psycologist ,as his behaviour has not improved
We now believe that he HAS seen some form of sexual activity whether on t.v. or at home ,he is seeing physcologist and other help as I cannot do this on my own .Thank you for you advice