Gigi Hadid and Zayn Malik have been enjoying every moment of parenthood following the arrival of their daughter Khai in September.MORE: Zayn Malik makes incredibly rare comment about baby daughter KhaiAnd soon, the celebrity couple's baby girl will be getting a playmate with the news that the One Direction star's sister Safaa is expecting her second child with husband Martin Tiser.The 18-year-old took to Instagram on Thursday to announce the happy news alongside a picture of a sonogram and a