As if losing a child isn’t heartbreaking enough, imagine being told the child you buried isn’t even yours. That’s no nightmare, but instead reality for a Brooklyn couple. Justyna and Rafal Sliwa shared their story through tears and with their attorney by their side. The horrible mix-up they said was the fault of the New York City Medical Examiner’s office and Bellevue Hospital and they’re holding everyone, including the city of New York, responsible in a claim filed Thursday for $5 million.