Millie Smith and Lewis Cann found out they were having twin girls, but only one of them would survive.

Smith gave birth to identical twins Callie and Skye on April 30, following a high-risk pregnancy that lasted 30 weeks. Skye only lived for three hours.

Without her sister, Callie spent the night in the NICU incubator under the watchful eyes of her adoring and distraught parents.

An exhausted mother of healthy newborn twins candidly told Smith that she was “so lucky” not to have two infants.

The statement devastated the new mother, leaving her at a loss for words. Then she saw the purple butterfly and knew that Skye’s legacy was to comfort other bereaved parents.

Millie Smith and her partner, Lewis Cann, welcomed their first child in November 2015.

Smith, who was expecting twin daughters and whose family includes many sets of twins, reported a “gut feeling” that she was carrying more than one baby.

The British parents were shocked to find out that one of their unborn children had a deadly disease less than two weeks after they discovered they were expecting twins.