Chris Martin was surrounded by loved ones as he rang in his 40th birthday. On Thursday, his ex wife, Gwyneth Paltrow, commemorated the special day by posting a sweet note on social media. "HAPPY 40th BIRTHDAY to the best daddy in the world!!!" she wrote alongside a selfie of them with their kids, Moses and Apple. "We [love] you so much." The post comes just a day after Gwyneth went Instagram official with her boyfriend, Brad Falchuk. Although the couple has been quietly dating since she "consciously uncoupled" from Chris in 2014, her birthday note to the American Horror Story co-creator was the first time she publicly acknowledged their relationship on social media.