"As a family, no words can express the sorrow we feel over the loss of Jovan and Kasandra," Lawrence read aloud.
She said the family is "overwhelmed with both sadness and confusion," and extends thoughts and prayers to the Perkins family.
Belcher's niece, Quaresha Boston, said the football player "embraced life and excelled at all he put his energy behind" and that God alone could "mend our hearts."
"We loved Jovan. His kindness, humility, respect and gratitude for family and friends were steadfast," she said. "... He was happy to be a new father and both he and Kasandra loved Zoey greatly."
AP Sports Writer Dave Skretta in Kansas City, Mo., and AP Writer Frank Eltman in West Babylon, N.Y., contributed to this report.