Maybe, probably. Is he looking for more monthly retirement income? And would he be OK with the reduction in liquidity?
Let's suppose for example he has $30,000 sitting in bank accounts. If he takes half that amount ($15,000) and deposits it into his CPF Retirement Account, he'll earn anywhere from 4% to 6% interest on that money (depending on where he's at in terms of bonus interest). That's tremendously better interest than he's getting with his bank accounts. He would still have $15,000 available for any immediate cash needs in this example. His CPF Retirement Account would then generate monthly retirement income — either with a definite end date (classic Retirement Sum Scheme) or guaranteed for the rest of his life (CPF LIFE) depending on his choice of payout plan.
He may be eligible for some government matching funds, so that sweetens the deal. And if you deposit up to $8,000 into his CPF Retirement Account then you're eligible for tax relief (a reduction in next year's income tax bill) — even if he's handing you $8,000 in cash and then you make the $8,000 top up into his RA. Same with your siblings and other qualified family members if applicable — many/all of you may be eligible for tax relief.