name change

What is the name of your state? colorado
I have two daughters(by marriage) age 13 and 14, their biological father is not around but religiously sends child support which we count on as income for our family. My girls want to have the same last name as me and my wife which we all agree is for the best. what is the best way to do this (economical and easy)

Call your local courthouse and ask for the forms for a name change for a minor. I think you have good grounds for the name change without bio-dad's consent. You're basically the dad, and having the same last name will create unity. There will be a fee, but it shouldn't be too bad. Just look up the courthouse and they can tell you where to go.

You would have to legally adopt them in order to change their last name to your's. and you would have to have the consent of their bio-father or prove that their had been a certain amount of seperation time which I am not sure what that would be for your state. but Here where I live it is for a period of one year. and sense you state that the bio-dad sends cs faithfully you would most likely have to have his consent in order to have this done.