—buenos días, señora méndez. ¿es tina su sobrina? —sí, mi esposo y yo tenemos dos sobrinos, tina y pedro son sobrinos.

The right possessive adjective in the conversation is:

- Buenos días, señora Méndez. ¿Es Tina su sobrina?

- Sí, mi esposo y yo tenemos dos sobrinos, Tina y Pedro son nuestros sobrinos.

Explanation:

The translation of the conversation is:

- Good morning, Mrs. Méndez. Is Tina your niece?

- Yes, my husband and I have two nephews, Tina and Pedro are our nephews.

The possessive adjectives are used to mention the direct or indirect ownership from something or somebody, these must be linked to the noun who realizes the action. The adjectives taking into account the personal pronoun are:

As the holders in the conversation are Mrs. Méndez and her husband, the personal pronoun that must be revised is "nosotros," and since "los sobrinos" are a male and plural noun, the form used must end in "os," therefore the correct adjective is "nuestros."