i-864 help with the annual income on taxes (SSN spouse benefit)

[Aquila Piacentini 1]

I am using my mother in law 1040's to fill out the i-864. A question came up as with her yearly annual income.

 

On her 2017 1040, shows that she has a "x" as her total income. That amount is based on her wages and a social security benefit. The wages are hers, from her job. The social security benefit is from my father in law (her spouse), as he is retired by disablement and gets money from social security. They do their taxes together but my father in law, who receives the social security benefit, is under her, as she claimed him in 2016. 

 

The total income (her wages + social security benefit) that she has on her 1040 is enough to cover the Poverty Guidelines of form i-864p. If I take the social security benefit amount out though, the income is not enough to meet the I-864 requirements. 

 

The question is if I should do a I-864a separately to my father in law, who receives the social security benefit, even if he is under my mother in law, who is the main sponsor. 

 

Just as an additional information... on my mother in law 2017 W2, a very similar number as the one in the 1040 shows up, but the W2 is only for her and her husband's name is nowhere there... which makes me believe that an additional i-864a is not necessary.