By Mia O’Hare JLS star Aston Merrygold has welcomed his third child into the world – a baby girl! The singer shared the exciting news with his followers after his wife Sarah Lou gave birth. Aston and Sarah Lou are already proud parents to two sons – Grayson and Macaulay – and now the pair have welcomed a new addition to their brood. The loved-up couple announced their pregnancy with a sweet video on their Instagram page. The clip began with their two boys Macaulay and Grayson sat on the sofa as Sarah asked: “Have we got your attention?”, before Aston added: “Because we want to tell you somethi…