As I stated, my wife and step daughter do not have any ties to the US but I'm trying to find out if I can claim them as dependents.
To claim someone as a dependent they must have either a Social Security number or an ITIN issued by the IRS.
If you are a US citizen and your spouse does not have a Social Security number or an ITIN and you are not applying for an ITIN with the tax return then you can only file your tax return as Married Filing Separately. Where asked to enter the spouse's Social Security number enter 999-88-9999. You can only print and mail your tax return, it cannot be e-filed. When you print the tax return erase the Social Security number for your spouse and manually enter NRA for non-resident alien.
Your spouse would only need to report her income if you were filing your tax return as Married Filing Jointly, applying for an ITIN with the tax return and you would be providing a statement with your tax return that you want your Nonresident Alien Spouse Treated as a Resident. See IRS Publication 54 Tax Guide for U.S. Citizens and Resident Aliens Abroad pages 6 and 7 - https://www.irs.gov/pub/irs-pdf/p54.pdf