Billie and Clint Dunn have two children, Haley and David, who is 16.
Chloe was born to Clint Dunn and Naomi Stewart just months before Hailey disappeared on Dec. 27.
"When I was pregnant with Chloe we thought she was a boy, and Hailey prayed and prayed for a little girl," Stewart said.
As a baby, Hailey looked almost identical to her little sister, Stewart said, and Hailey called her "Mini-Me."
Stewart believes Chloe is also feeling the anxiety of having her big sister missing, since ythe tow played together every day.
"Doctors say that would be normal," Stewart said. "Everybody has a different type of trauma, (including) babies."
Stewart says until Hailey's return, memories are keeping their hopes alive.
"Hailey tickled her nose and Chloe laughed for the first time. I've had that playing over in my mind, waiting and wishing it would happen again."
Clint Dunn and Naomi Stewart continue passing out fliers in West Texas, hoping someone will have information about Hailey.