Kenny and Billy are brothers. Both are divorced and have been for many years. Kenny has a child, Philip (9), and Billy has two children, Margo (11) and Jack (13). Each of the brothers pay half of the rent and utilities for their house, but pay for all other expenses for their respective children. All the children lived with their dads in the same house all of 2021. They all have separate bedrooms. Both of the brothers' ex-spouses pay child support. Who can file as head of household?