Ms. P (grew up in Columbia, MD) pronouces all three the same. Daughter, born in NYC but raised inside the DC Beltway, pronounces Mary and marry the same, but merry differently. Son, born and raised in the DC suburbs, pronounces all three the same.
Yes, thank you, that was the name.
Perhaps it has to do with the quirks of English spelling, which do ultimately have an effect on speech patterns. “Ear” is spelled ike “bear” but “bear” rhymes with “air” and “bare” while “ear” rhymes with “bier” and “beer”, but looking at the way they are spelled might lead to some confusion.
Around here, we seem to have the merry/marry/Mary merger, where the vowel sound is approximately “eh” (a short e, not a long a) but wanders enough that we draw the meaning from context, not strict pronunciation. We generally have a fairly sloppy way of speaking, but I feel as though more content is extracted from the melody of an utterance than from the precisely-formed word sounds.
It seems to have something to do with the Great Vowel Shift, but it’s not clear really what happened: