I have three kids, currently in 9th, 10th, and 12th grade. Started a 529 on autopilot for the oldest many years ago, and through regular contributions and the recent run-up in the stock market, it is now larger than my son's anticipated costs. I have 529s for the others, but they are much smaller. I know I can change beneficiary on an account, but what if I want to use money from my oldest's account for my middle son before the oldest has finished college? Can I somehow split an account, or otherwise manage this creatively?