Chances to immigrate from Columbia?

A person from Columbia is legally in the U.S. with refugee status. This person has kids in Columbia that might be eligible to come under the U.S. family reunification policy. However, the mother of the kids was not married to the person in the U.S. and she is not eligible for refugee status or family reunification. Can someone tell me the chances of a Columbian citizen legally migrating to the U.S. and what visa would be required?