If he got a 1099, then its taxable income. Depending on the amount, it may also make part of his social security taxable. There's no general exemption for age.
The general rule is that a return of his premiums will not be taxable if he paid them after tax, but if he got more than he paid in premiums (treating this as whole life or any other investment gains) then the extra is taxable income. Or if the premiums were paid tax-free (like a non-taxen employee benefit) then the entire amount is taxable.
If you think the amount on the 1099-R is incorrect (incudes his after-tax premiums), you can report less income, but you would have to be prepared to prove it.
