Amy S. Foster is not letting a 48-year age difference nor a (possibly) tumultuous past get in the way of her defending her little brother Rennie and her dad, famed music producer David Foster. David, 74 shares a 2-year-old son with his wife Katharine McPhee and recently posted an unbelievable video of Rennie drumming to Michael Jackson’s “Rock With You.” As one commenter pointed out, it’s more than just your typical toddler banging on a drumset with reckless abandon.