He did have a daughter, whom he had custody of at the time of his arrest in March of 2012. Not much is known about her publicly - and for good reason. Being the daughter of Keyes, a confirmed murderer and the suspected serial killer comes with a heavy load.
As Melissa Moore, daughter of convicted serial killer Keith Jesperson (The Happy Face Killer) wrote for the BBC in a 2014 article titled 'My Evil Dad: Life As a Serial Killer's Daughter' - "Somehow I ended up feeling that I had to pay restitution for his crimes. I felt dirty, I felt less of a person, I felt isolated, I felt alone."
The best thing onlookers like you and I can do for the children of serial killers, murderers and other types of criminals is to view them with compassion just as you would any other victim. Indeed, they are.