Here's why:
* Redundancy: The phrase is redundant, as it uses the same word twice to refer to the same person.
* Informal and Casual: It is sometimes used in informal, casual speech, but it is considered grammatically incorrect.
* Misunderstood: Depending on the context, it could be misunderstood as referring to two different people.
Instead of "tu y tu," you should use:
* Tú y tú: This is the correct way to refer to "you and you" in Spanish.
* Ustedes: This is the formal plural pronoun, referring to "you all."
* Vosotros/Vosotras: This is the informal plural pronoun, referring to "you all" (used mainly in Spain and some Latin American countries).
Example:
Instead of: "Tu y tu, vamos a comer." (You and you, let's eat.)
You should say: "Tú y tú, vamos a comer." (You and you, let's eat.)
or: "Ustedes, vamos a comer." (You all, let's eat.)