Nikolas Cruz Real Parents

Was Nikolas Cruz biologically related to his brother Zachary and will we ever find out who their biological parents are if so?

From the different news reports I have gleaned Nikolas and Zach do have the same mother, but different fathers.  Nikolas was adopted first then when the woman got pregnant again with Zach. The Cruz's adopted him as well.

To my knowledge their biological mother or fathers have not been found.