Melissa Mae Carlton and her family are dealing with an unimaginable loss … announcing the death of their daughter Molly, less than two years after their daughter Abigail passed away.

The faith and grief influencer announced the heartbreaking news in an Instagram post Friday … revealing Molly died on Christmas Day — and adding the family was in total shock and disbelief at her sudden passing.

Carlton notes Molly often expressed a desire to see her older sister again … which she says gives her a small sense of comfort because they’re now reunited in heaven.

Carlton followed up the announcement with a post clarifying the cause of death … explaining doctors believe Molly may have suffered from a genetic heart condition — which may have also affected Abigail, who ultimately died of sepsis.

She explains they didn’t know this information about Abigail before because she died so suddenly, doctors couldn’t evaluate her in the hospital … while Molly was analyzed in such a setting.

Abigail was 9 when she passed. They haven’t revealed Molly’s age.