Nick, Aaron's Sister Leslie Carter Dead at 25

"House of Carters" reality star Leslie Carter -- younger sister of Backstreet Boys singer Nick Carter -- died yesterday in New York at the age of 25 ... the family confirms.

The Carters released a statement saying, "Our family is grieving right now and it’s a private matter. We are deeply saddened for the loss of our beloved sister, daughter, and granddaughter, Leslie Carter. We request the utmost privacy during this difficult time.”

The details surrounding Leslie's death are unclear.

Leslie was an aspiring singer, who gave birth to a daughter back in April.