As the robot used to say, "Danger, danger Will Robinson!"
Damned if you do and damned if you don't.
If you want to take the high road I would sit down with each girl and tell them that you will match whatever funds their natural father gives them. No more, no less. If they cannot get any from their dads you should be under no obligation to help. It is their mom's and dad's place to pay for their education, not the new step dad of three years. If the dad's cannot help you can still come out morally ahead by giving them "some" money to get them started. But you should not pay it all. This cannot be one of those, "I'm gonna quit work, go to school, and when I finish I will get a great job making lots of money" deals either. They must work their way thru. I would also make the checks out TO THE SCHOOL!
I have seen siht like this many times. Seen guys pay off a house for the new wife, pay off the wife's ex-husband's truck, pay for a surgery, pay off credit cards, and so on and then get handed divorce papers the next week. BE CAREFUL!!!!
RSKY
Oh and one of the guys that got screwed over and divorced after paying off the new wife's ex's truck and credit cards helped raise her daughter. He helped put her thru school AFTER the divorce, gave her away at her wedding (instead of the natural deadbeat dad) and has a better relationship with his step-daughter than that that step-daughter has with her mother. You just never know.