i was a single mom with my first son, and his father and I went our seperate ways before he was born. He is now 17 and this has not been an easy thing for him. I will give you this advice- don't lie. he needs the truth, but at appropriate doses as he grows up, unless it's true that he's sick, in the way your son has it pictured, don't tell him that, because if your story ever changes in the future he will wonder what else you lied about, and he needs to be able to trust you and your word! It ok to say, your dad just isn't able to be here, i'm not sure where he is, but sometimes daddy's can live at home and sometimes they just can't. and then focus on what he does have, God, you or grandparents or your close friends, etc. and keep your comments about him neutral, not negative. i don't know his history or why you don't want him around, but you have to remember-he is a part of your son's identity, so be careful what you say, again you don't have to make him out as a saint, just save the neg. comments for a friend, not your son. He will long for him and probably create a fantasy picture of him, and have lots of questions, again because he is his son. so any facts, pictures that you can share for his identity sake can't hurt, like you got your hair or eyes from ???. I also tried to explain as he got older thet some men help to make a baby, so they are a biological father, but some men take care of and raise a baby, and that's a daddy. and some men do both.That helped when i later met and married my husband of 13 yrs. I was able to say, beacause he was asking why so and so had a daddy and he didn't. I told him the man that helped to make you just couldn't be your daddy, but God has put My husband in his life to be his daddy. This is not ever going to be easy because it's not natural for the dad to not be there, but you and him can learn to deal with it in a positive way and hopefully grow closer together- just be honest!