As my daughter Harper and my son Liam take it in turns to go down the slide, they both look over at me and wave. ‘Mummy, watch us,’ they shout in unison. As I watch on proudly from the park bench, alongside my husband John, it’s hard to believe that we finally have the children we dreamt about for so long. Both conceived through IVF, our children are medical twins. They share the same brown hair and big grins. They look so alike. But what makes them unique to other twins is that Harper is six and Liam is three - they were born almost three years apart. To everyone else, they just look like normal siblings, but
