You only have to have a short conversation with any therapist to realize that there are a heck of a lot of parents out there who are not particularly good at the job of parenting. There are plenty of ways to screw up a kid, and not all of them enable a redemption arc as they get older. 

Still, often being a truly reformed parent is better than a child having no parent at all. This can be especially true in the case of families where fathers were not aware of having children until later in their lives. While there is no guarantee that a surprise kid will suddenly turn a man into a model father, those who truly make the effort can have something to offer. It may not be an easy situation, but it can be made easier with the help of a positive attitude and some effort.