"your father and your mother"
Translation:ваш папа и ваша мама
By 'accent mark' do you mean "й"? Й, is it's own separate letter, not just an optional accent on "и". :) And in this case, typing "твои" instead of "твой" changes the word. "Твой" means one masculine thing belongs to you, and "твои" means several things belong to you.
Also the pronunciation is not the same, й is shorter than и, but more importantly, й makes diphthongs, that is, it "sticks" to the preceding vowel creating a single syllable. I believe that it is the only Russian vowel (although it is not "really" a vowel) with that property, that is, there is never more than one vowel per syllable in Russian, unless the й is involved, which always sticks to the neighboring vowel. So твои, which is plural, is two syllables: тво - и, "tva - i" with the accent on the second one, и. While твой, which is masculine singular, is a single syllable in pronunciation: твой, "tvoi", with a short i. I believe that's why Russians struggle to pronounce the english "w" and end up pronouncing a "v" instead: "wa" sounds "more or less" like a "ua", with both vowels together in a single syllable, and there is nothing similar in Russian, since й is so far as I have seen the only diphthong-enabled vowel.