Correct usage of "must have to"

Question

The construction 'must have to' is used in this sentence:

Oh, it is locked. We must have to have the key to open it.

Is this correct? Is there a better alternative phrasing?

Answer 1

In most cases, must and have to mean the same thing, so this is redundant.

^✲Oh, it's locked. We have to have to have the key to open it.

The only situation in which you would use both expressions is if you are using must in the 'epistemic' sense of (approximately) "appears very probable that" or "is my confident inference that"

Oh, it's locked. I conclude that we have to have the key to open it.

But that's really semantic overkill for conversational usage! I think most people would say simply:

Oh, it's locked. We need the key.

---

^✲ marks an utterance as unacceptable

Answer 2

Its a kind of deduction When we say:

oh,we are starving,we must have to stop to eat something.

it means that we are very likely to be forced to stop