The fact that they are filing taxes themselves does not mean you can't claim them. They would need to indicate someone else could claim them when they file their returns. You would need to provide a lot more information as to their age, whether they are full time students, income levels, who paid for the majority of their support, etc... if you are asking if they still qualify as dependents. You can review IRS Pub 501 section on qualifying dependents if you have questions about that.
https://www.irs.gov/publications/p501/ar02.html#en_US_2016_publink1000220886
