There can't be two Heads of Household in one residence. You would have to be the Head of your own Household. Ideally, you would want an entirely separate residence. However, there are provisions for someone in your circumstances. You would need to show that your portion of the house was an entirely different household from the rest of the house.
See https://www.irs.gov/pub/irs-pdf/f14824.pdf
Costs for keeping up a home test.
