San Antonio boy sings 'Coco'-inspired serenade at baby sister's altar in heartwarming video

A San Antonio boy plucking the strings of a toy guitar in a serenade to his late baby sister for what would have been her first birthday is winning hundreds of thousands of fans online.

Samir Deais and Stephanie Deais caught video of their son, Alexander, singing "Remember Me" from the hit movie, "Coco," to an altar dedicated to his baby sister, Ava Lynn.

His parents told mySA.com that Ava Lynn was born with hydronephrosis, a kidney condition, and passed away last May. She was 4 months old.

Samir Deais said the movie, which depicts the tradition of Dia de Los Muertos, helped 4-year-old Alexander cope with the family's loss. The entire family was moved, especially by this song.

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Samir Deais shared this family photo showing himself, wife Stephanie, son Alexander and daughter Ava Lynn. Samir Deais shared this family photo showing himself, wife Stephanie, son Alexander and daughter Ava Lynn. Image 1 of / 32 Caption Close San Antonio boy sings 'Coco'-inspired serenade at baby sister's altar in heartwarming video 1 / 32 Back to Gallery

"I couldn't be more thankful for the movie," Deais said. "It's made it so easy to understand for him and for us to explain to him in a beautiful way."

Deais tweeted the clip of Alexander singing to Ava Lynn's photo on Dec. 30 —it has returned more than 90,000 likes, 30,000 retweets and nearly a million people have watched the video. Alexander had no clue he was being recorded, Deais said.

He said the reaction "has been nothing short of beautiful."

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"All this ugly in the world and these kinds of things make it still seem beautiful in the dark times," he said. "All these blessings for our small family make us very humbled and thankful and blessed."

They were "brought to tears" by the support they've been shown.

"Alexander has seemed to brighten us all," Deais added.

He said they are expecting a third child, who has already been named Stella Grace.

Madalyn Mendoza is a digital reporter for MySA.com. Read more of her stories here.| mmendoza@mysa.com | Twitter: @MaddySkye