Well, I did find this discussion on determining household size, which is why I raised the question:
Determining Household Size
"The size of your household is very important: The more members you have, the less likely it is that your income will exceed the state median for households of the same size, and the less likely you are to have to take the means test.
For example, assume that your current monthly income is $6,000, the median income for a household of three in your state is $5,800, and the median income for a household of four is $6,500. Being able to count that additional person means you won’t have to take the means test.
Unfortunately, neither Congress nor the courts have given clear guidance on how to calculate household size. Most courts adopt the census test for a household, which includes all of the people, related and unrelated, who occupy a house, apartment, group of rooms, or single room that is intended for occupancy as separate living quarters. Under this test, you can count your children or stepchildren even if they are not your dependents for tax purposes."
This discussion appears to indicate that you claim people residing in your household for the means test even if you cannot claim them as dependents for tax purposes.

