She added that the Canadian musician was more concerned with raising the Jenner boys during his 14-year marriage to their mother, Linda Thompson.
David 70, recently wed much-younger singer Katharine McPhee, married Linda, 69, in 1991 following his 1986 split from Erin, 37, and Sara’s mother, Rebecca Dyer.
"We were dealing with our whole own emotional turmoil, which was watching our father raise other children,” Sara, 38, explained referring to the adult sons of Linda and Caitlyn Jenner.
"That was the thing that kept me up at night," Sara admitted.
"We never lived with our dad right after our parents broke up,' Erin explained. "So from the ages of three and five we were living with our mom, and our dad was living in this $20 million house with Brandon and Brody. It had the trolley, it had the pool."
Erin revealed she carried some "resentment" towards the Jenner boys, especially because people had the misconception that she and Sara were the ones living an extravagant lifestyle.
"They had a very different life," Erin said of Brandon, 38, and Brody, 36.
"But out in the world, people would be like, 'You guys are spoiled brats and you guys have it all and you're rich kids,"' she continued. "And we would be like, 'I mean, yeah, but we don't live there. We don't have the gate code. We don't have a room there. We're not really a part of that world."'
Radar readers know Brandon is now an up-and-coming musician, while Brody is a star on popular reality show The Hills. Both hunks have also made appearances on Keeping Up with the Kardashians with their famous step-siblings.
"Mine was less resentment towards them, it was more like, we're misunderstood out in the world, because we have this fake, spoiled lifestyle, but we're not even really allowed to be a part of it; so, we get all the backlash for it, but we don't actually get the benefits,” Erin said of her rocky relationship with Brody and Brandon.