Employer contributions to eligible employee HSAs must be comparable.
Comparable contributions must be made to all eligible employees enrolled in a qualifying HDHP, are in the same category of employment (full-time, part-time, former employees, and collectively bargained), and the same category of coverage (self, self +1, self +2, self +3).
An employer must contribute the same dollar amount or percentage amount to everyone in the same category. Additionally, the higher coverage categories can’t have a lower contribution amount compared to the lower coverage categories. This means coverage for more than one person has to be greater than a single individual.
Source: IRC Section 4980G and the regulations thereunder at Treas. Reg. Sec. 54.4980G