1099-R Youngest Age you could have retired - disability question

[bordumsetzin]

My husbands mother passed away when he was a minor from cancer.  She was unmarried at the time and he was beneficiary of her retirement.  To this day, he gets a small monthly stipend/disability benefit, just as if he was the surviving spouse.  He will receive this for the rest of his life, just as a spouse would.   We have always received a 1099-R with Box 3 checked (disability).  What do I answer on the question about the youngest age he could have retired?  I am assuming that his mother would have to have been 55 for retirement (State of California employee) but because of this unique situation - I am no sure what to write.  Am assuming its all taxable until he reaches retirement age so until then it doesnt really matter?

[macuser_22]

The box 7 code might be wrong,  Payments to beneficiaries should have a code 4. 

The age question only applies to the employee (owner of the plan).

Ask the plan administrator.