How often do you see these grown step-girls aka Paris Hiltons? Do they live with you and bf often several times per wk. or what? Would you/your bf be expected to support them financially if their mother couldn't help them financially?

You have to ask yourself just how much energy you want to spend understanding these gals if they don't live underneath your roof.

Not sure if badgering bf about his daughters is going to work right now. Better that you refocus to distance yourself from step-daughters and renew your energy in other areas of your life.

Can I ask you this simple question: Could you, your daughter and stepdaughters be able to all prepare a nice meal for yourselves / do potluck? Start by a shared activity that requires their adult contribution in relationship to you (not your bf). They are adults after all and adult expectations must now be placed on them.