Dependent SSDI benefits

Hi,

 

Our 31yr old disabled son just started receiving SSDI benefits based on my wife's earnings record.  SSDI is his only source of income and amounts to less than $12k/yr.  My wife and I file MFJ, with our son as our sole dependent.  He lives with us year-round.

 

My question is whether his SSDI income, for which he will receive an SSA-1099, must be reported on a tax return, either our MFJ return or our son's own report (a tax return in his name has never been filed to date).

 

If the former, will it increase our AGI, and if the latter, will that preclude us from claiming him as a dependent on our MFJ report?

 

Not sure whether it matters, but his mother and I are his biological parents, court-appointed conservators and representative payees.

 

Thanks in advance!