No one can deny the fact of a relationship. In that sense, something of the former marriage may remain indefinitely. Certainly, this is especially true when the union produced children. There are many things which could render marital consent invalid. If we recall that the spouses are committing themselves, without any reservation or condition, to a life-long, faithful relationship that is open to children, we can see why in a culture as our own how frequently this is an issue.
Marriage is for people who are capable of making an adult commitment.
Not everyone may be capable of assuming the essential rights and obligations of marriage and family life. Everyone knows that children are not capable of marriage. We also know that those who are psychotic are not able to commit themselves. Certainly, other psychological factors may raise the issue of the capacity of an individual person for marriage. If someone cannot hold a job, or assume ordinary personal responsibilities, or can not communicate adequately on a personal adult level so as to share oneself with a spouse, then the capacity of that person for marriage becomes questionable.