I am a single mom and my son is one year old. His father is not involved in our lives and I was just curious if and when I should bring this up and how much information I should be disclosing to my son about why things didn't work out.
This is an issue that many moms struggle with but, in truth, there is no way to fully resolve the questions your son may have as he gets older. It is important to offer information as he grows, adjust your information to his age, and be ready for those questions to come up many times over the course of his childhood. He may have different feelings about this that change over time. It is not usually until 4 or 5 years old that children really begin to compare families and ask questions. He is too little at the moment to understand why he does not have a Daddy, so for now I would suggest reading lots of books that show him many different types of families. As he gets older, you can talk about differences in families, show him examples while you are out at the park, shopping or watching television, and try to socialize with people who live in all kinds of families.
It is important to be neutral when talking about his father--speaking about him in negative terms can make feelings of abandonment more pronounced. When he is ready, and you will know this by the questions he asks, you can let him know that being a father is a big responsibility and that his biological father was not ready. Make sure you emphasize that this has to do with his father and his issues, not your son. Share with your child any pictures or positive memories you have of his father, he will hold onto these over the years and it will be very important for him. In all these conversations remind him how much you love him, how much you always wanted him, with tons of hugs and kisses. Loving him well is the most important part of parenting. It is the most important thing in his life and, in truth, all he really needs.