The first useful step is simply understanding what income sources your parents will actually have — pension, EPF or NPS corpus, rental income, other investments — and whether that realistically covers their expected expenses, factoring in inflation over what could be a 20-30 year retirement. This isn't about taking over their finances; it's about having enough visibility to spot a genuine gap early, while there's still time to plan around it.
If a shortfall seems likely, options include helping parents build a more diversified retirement income (annuities, senior citizen savings schemes, or other structured income products), or having an honest family conversation about whether adult children might need to contribute financially, and how that would work practically and fairly if there are multiple siblings involved.
It's also worth discussing healthcare costs specifically, since medical expenses tend to rise both with age and with general healthcare inflation — ensuring parents have adequate health insurance (or planning for the cost if they don't) is often one of the most financially significant parts of this preparation, and one of the easiest to underestimate.