There is no limit on the number of people who can contribute to your HSA, however you still can't have total contributions exceed the maximum annual limit in any given year (including catch-up contributions if you are between 55 and 65 years old).
If anyone other than your employer contributes to your account, you will see the tax advantages, not the person making the contribution. That said, if your employer contributes to your account, you can’t take a deduction on your taxes, but you will not claim that as income either.
Don’t worry. We will take care of this during tax time!