Is it definitely true that "10 years or younger" only applies to spouses? IRS Publication 590-B seems to state otherwise (see below):
"Eligible designated beneficiaries.
An IRA beneficiary is an eligible designated beneficiary if the beneficiary is the owner's surviving spouse, the owner's minor child, a disabled individual, a chronically ill individual, or any other individual who is not more than 10 years younger than the IRA owner."
and
"If the owner died before his or her required beginning date (defined earlier), and you are an eligible designated beneficiary, you must generally base required minimum distributions for years after the year of the owner's death using your single life expectancy shown in Table I in Appendix B, as determined under Beneficiary an individual later."
