I filed my foster care children on my taxes, now the bio parents are making waves.. who has the right? We had them almost 8 months and placed by dept human services.

We filed our foster kids on our taxes.  The state took custody March 27 (2018), but they have been in our home since March 8 when they were removed from their bios home.  Now the bios want to file the kids on their taxes but they have not had them since March 8.  We have supported them since they came here, albeit bios provide a bill of groceries (less than 300.00) using food stamps and a couple boxes of diapers...they are claiming they supported them.  What case do we have and are we in the right or wrong?  There were 4 children.  We got emergency foster (custody / care) March 27, 2018 and had them until Oct. 22, 2018.  We had them removed and they were placed in other homes (first separated) then with the bio moms mother... If they were with us the majority of the year, who has legal right to claim on taxes?  Currently, the bios still do not have custody.