"They will fight this". Former Little Mix star Jesy Nelson has revealed that her twin baby daughters have been diagnosed with a rare genetic condition which means they will "probably never walk". The singer gave birth to Ocean Jade and Story Monroe Nelson-Foster prematurely last May with musician Zion Foster. On Sunday, Nelson said in an Instagram video that the girls have Spinal Muscular Atrophy (SMA), which she described as the "most severe muscular disease". SMA is a progressive muscle-wasting disease that can cause death within two years if untreated. At present in the UK, screening for SMA is only carried out on those who have a sibling with the condition. Tap the link in BBCNews's bio to read more about SMA and Jesy's story. (📷 Getty) #JesyNelson #BBCNews