Around 3 years old a child can start to understand what you say. All children have different emotional maturity levels and you can gauge it from there. By the time they enter school they are able to compare and comprehend what other people tell them and by this time you really should be honest.
Is there a reason that the father cannot see him? Can he have contact with him via phone or anything? By saying the father is too busy, he may feel like he is not important. Sometimes the truth is better than the lie.
Good luck - being a parent is the best hardest thing you will ever do.



