Jesy Nelson, a one-time member of the British girl group Little Mix, is opening up about the rare genetic condition her children are facing.

Parents of babies born with a life-limiting, rare condition say their diagnoses came months too late, and after they had initially raised the alarm about their symptoms.

Nelson said the twins had been diagnosed after four months of “gruelling” hospital appointments, and she wanted to raise awareness of the condition and the signs to look out for because “time is of th...