Is it okay to have 2 characters that starts with the same letter? Like Malia and Mason?

No, that directly violates Article 57 of Section 9 in "Rules for Writers." Sorry.

Change mason to Matthew, makes more sense.

No, it's not, which is why Lewis Carroll was guillotined by Queen Victoria after he wrote a book containing the characters Tweedledum and Tweedledee.

yes, but those names are both from the tv show teen wolf. Is that where you got them?

no

Why wouldn't it be? Am I missing something here??