A 9-year-old relative of Kansas City Chiefs owner Clark Hunt was one of the dozens who tragically passed away in the Texas floods over the weekend.

Janie Hunt -- the great-granddaughter of William Herbert Hunt -- was attending Camp Mystic near the Guadalupe River in Kerr County on Saturday when the sudden rise in water took her life, her grandmother told the New York Times on Sunday.

Janie was at the camp with several of her cousins, who were able to make it out safe, her grandmother added.

Tavia Hunt -- Clark's wife -- took to Instagram to mourn the loss ... writing, "Our hearts are broken by the devastation from the floods in Wimberley and the tragic loss of so many lives -- including a precious little Hunt cousin, along with several friends' little girls."

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In her heartbreaking post, Tavia shared several messages that encouraged those to lean on their Christian faith to get them through.

The floods have killed at least 81 ... and rescue efforts to find others still missing remain ongoing.

The NFL's two Texas-based teams, the Dallas Cowboys and the Houston Texans, pledged to donate $1.5 million in conjunction with the NFL Foundation to help in recovery efforts.

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The Cowboys added in a statement on Sunday their "hearts are heavy" over the "devastation and loss of life caused by the floods."