What? You are confused about the 'Uncle' part?
Gwen and her hubby, Coldplay frontman Chris Martin, are very close friends with Beyonce and Jay-Z. Thus the kids now refer to the singer and father of Ivy Blue as 'Uncle.'
Paltrow tweeted fans from the concert, “Yup. Uncle Jay at the O2,” and shared a picture of her kids doing Jay-Z's infamous diamond hand sign.