Kevin Federline claims an explosive argument over breastfeeding is what led to his divorce from Britney Spears. In an excerpt of his upcoming memoir, You Thought You Knew, obtained by Us Weekly on Thursday, the dancer claims he walked in on Britney doing cocaine - when she was still breast-feeding their infant kids! Kevin alleged this happened at a release party for his album Playing With Fire in 2006. Britney had originally said she'd stay home with the kids, Sean Preston and Jayden James, who were just 13 months and 1 month old at the time, respectively.