their is haiden

haiden = their (possessive pronoun) (some things Google found for "haiden": a common term; an unusual to uncommon last name; an unusual to uncommon masculine first name (perhaps a form of unisex name Hayden); Haiden Surf boys swimwear; the hall of worship of a Shinto shrine; a Gewürztraminer variety of white wine grape; in Finnish means genitive plural of shark; name of places in Germany and Austria)

Word derivation for "their":
Basque = haien, beraien
Finnish = heidan + -nsa or -nsä
Miresua = haiden

This ends pronouns for now. I still have it and its to do, but I want to think on those for a while.

your (plural) is teuden

teuden = your (plural) (possessive pronoun) (some things Google found for "teuden": an unusual to rare term; user names; a rare last name; name of a World of Warcraft character; similar Teufen is the name of a places in Switzerland and Germany)

Word derivation for "your" (plural) :
Basque = zuen, Finnish = teidan + -nne
Miresua = teuden

I need to deal with the letters I have in the Basque and the Finnish words. My possessive pronouns in Miresua are inescapably somewhat irregular.

our is geiren

geiren = our (possessive pronoun) (some things Google found for "geiren": an uncommon to rare term; a rare last name; a very rare first name; user names; name of a World of Warcraft character; name of a place in Norway)

Word derivation for "our" :
Basque = gure, Finnish = meidän + -mme
Miresua = geiren

In Finnish, -mme is a possessive suffix appended to the main word owned, which is used used with or without the genitive meidän.

I considered making this word gemen, to use an M from Finnish, but that would have made my possessive pronouns even more irregular. M will appear in the ending for most 1st person plural verb conjugations.

his/her is hären

hären = his/her (possisive pronoun) (some things Google found for "hären": an uncommon term; HÄREN bath towels and washcloths by IKEA; similar Haren is an uncommon last name, notably Major League Baseball pitcher Dan Haren; similar Haren is an unusual masculine first name; in Danish and Swedish similar haren means hare (lepus); similar Haren is the name of places in the Netherlands, Belgium, Germany and Somalia)

Word derivation for "his/her" :
Basque = haren (or beraren), bere
Finnish = hänen (genitive) + -nsa or -nsä (possessive suffix)
Miresua = hären

My Miresua word is unusually close to the Basque word, haren, and also to the Finnish word, hänen.

In standard Finnish, both the possessive suffix and the genitive of the personal pronoun are apparently compulsory. In colloquial Finnish, usually only hänen (the genitive) is used. The possessive suffixes differ depending on front or back vowel harmony.

Miresua doesn't feature vowel harmony. (Although my experimental Hungarian/Finnish artlang, Samgur, does.)

In Basque, bere is reflexive, meaning his own, her own, plus its own.

your (singular) is zunen (revisited)

zunen = your (singular) (possessive pronoun) (some things Google found for "zunen": an unusual to rare term; a rare last name; a rare first name; user names; ZUNEN is a navigational waypoint in Texas; similarly named Zune music + video software; seems to be a form of sun or sunshine in Yiddish (transliterated))

Word derivation for "your (singular)" :
Basque = zure, Finnish = sinun + -si
Miresua = zunen

In Finnish, sinum is the genitive form of the personal pronoun and -si is a possessive suffix appended to the word owned.

My previous Miresua word for your (singular) was ziru. I posted that word only ten days ago. Guess I wasn't looking at the big picture. This time around there's more logic, less irregularity. And my words are still valid alphabetic mixes of the Basque and the Finnish words.

my is miren (revisited)

miren = my (possessive pronoun) (some things Google found for "miren": a very common term; Miren Browser for Android Phone; a uncommon feminine first name which is the Basque form of Mary or Miriam, notably Spanish actress Miren Ibarguren; a rare feminine first name which can be Irish; "Miren, the Moaning Well" is a rare game card in Magic: The Gathering; an unusual last name; third person conjugations of the verb "to look" in Catalan, Spanish and Galician; name of a place in Slovenia on the border with Italy; name of places in Indonesia and Poland)

Word derivation for "my" :
Basque = nire, Finnish = minun + -ni
Miresua = miren

I'm redoing this word, which I just did only ten days ago, to make my possessive pronouns more regular. Proof again that I change my mind on words. My previous Miresua word for my was nime.

The genitive case ending for Miresua will be -n or -en. That I'm in addition using the r from the Basque word shows that possessive pronouns will be somewhat irregular.