While it is possible for two families to live under one roof to each claim HOH, be prepared to produce proof to the IRS that true separation exists - each family pays it's own expenses, share of rent, upkeep, food, etc.
https://ttlc.intuit.com/questions/3016633-can-two-people-claim-head-of-household
There have been some tax court ruling on this in the taxpayers favor after the IRS disallowed it when the taxpayers have shown that their living situation is separate and each was able to prove they paid more than half of their portion. That does not mean that all facilities must be separate such as kitchen and bathrooms.
Keep good records since the IRS often will question two HOH at same address.
**Disclaimer: This post is for discussion purposes only and is NOT tax advice. The author takes no responsibility for the accuracy of any information in this post.**
