A grandfather who allegedly dropped his 18-month-old granddaughter from the 11th floor of a cruise ship docked in Puerto Rico will change his plea to guilty, his lawyer says.

Salvatore 'Sam' Anello, 50, was charged with negligent homicide after Chloe Weigand fell from an open glass window on-board the Royal Caribbean Freedom of the Seas ship in July.

He and his family insist it was an accident, claiming he hadn't known the window was open when he lifted the toddler up to bang on the glass - a game she liked to play at home.

But the family's lawyer said on Wednesday that Mr Anello would now plead guilty to the charge in order to avoid jail time.

"This decision was an incredibly difficult one for Sam and the family, but because the plea agreement includes no jail time and no admission of facts, it was decided the plea deal is in the best interests of the family," Michael Winkleman said in a statement.

FAMILY SUES CRUISE COMPANY

In an interview with the US version of TODAY last year, Chloe's parents, Kimberley and Alan Wiegand, said Mr Anello had been "very, very distraught" ever since Chloe's death.

"You can barely look at him without him crying, she was his best friend," Mr Wiegand said.

The family is now suing the cruise ship company, accusing it of negligence by allowing the window in the ship's children's play area to be open.

"We still maintain this was a tragic, preventable accident that never would have occurred if Royal Caribbean followed the industry-standard window fall prevention codes that are designed for the singular purpose of preventing children from falling out of windows," Mr Winkleman said.

"I just remember screaming 'I thought there was glass, I thought there was glass'," Mr Anello told CBS in November.

"I still say it to myself. It's just, I kind of relive it all the time and I just thought there was glass there. I don't know what else to tell you.

"It seems like it's all not real. She's such a beautiful little girl. Perfect little girl."

RELATED: Grandfather reveals he is colourblind

Anello appeared in court in San Juan, Puerto Rico, on Monday, where he declined his right to a jury trial.

His four-day trial had been scheduled for April 2.