Question: Let's say we have this:

> 
> Yo sé.  
> 
>  Tú sabes.  
> 
>  Él sabe.  
> 
>  Nosotros sabemos.  
> 
>  Vosotros sabéis.  
> 
>  Ellos saben.
> 
> 
> 

So far so good. However:

> 
> Tú y yo sabemos. --> Person: Nosotros?  
> 
>  Tú y él sabéis. --> Person: Vosotros?  
> 
>  Nosotros y ellos sabemos. --> Person: Nosotros, why not ellos?  
> 
>  Tú y todo el mundo sabéis. --> Person: Vosotros, why not ellos o nosotros? 
> 
> 
> 

It looks like there is an established order between persons, is it so?  

How do we know which one to use when there's many different persons?  

E.g. *Ellos, yo y tú mismo {sabemos? sabeis? sabes?}*.

Answer: 
### Castellano

Sí, hay una prioridad con las personas a la hora de concordar el verbo, lo he descubierto investigando para [mi pregunta](https://spanish.stackexchange.com/questions/22087/concordancia-del-verbo-en-sujetos-compuestos) sobre sujetos compuestos. La primera persona tiene prioridad sobre las demás y la segunda la tiene sobre la tercera.

En [Wikilengua](http://www.wikilengua.org/index.php/Concordancia_entre_sujeto_y_verbo) leemos:

> 
> Si los sujetos son de distinta persona, el verbo concuerda en plural
>  con la persona que tenga prioridad (la primera persona tiene prioridad
>  sobre la segunda y tercera; y la segunda, sobre la tercera).
> 
> 
> *Juan y yo iremos al cine, así que tú y Olga tendréis que esperar un rato hasta que lleguemos.*
> 
> 
> 

---

### English

Yes, there is a priority with people when it comes to agreeing with the verb. I found out while investigating for [my question](https://spanish.stackexchange.com/questions/22087/concordancia-del-verbo-en-sujetos-compuestos) about compound subjects. The first person has the priority over the other, as well as the second over the third.
It all depends on what you want to emphasise. 

Tu y yo sabemos = Nostros sabemos. 

The thing is that when you say "nosotros" it could be an unlimited number of people. Let's put an example: 

* Me and you know he is cheating on her .- Here the emphasis is that you and me know something. I am not talking about other people
* We know he is cheating on her. .- Me and you know it but there could be other that know it too.

**There is not and established order between people**. However, as @blonfu points in the comments, the use "yo" the last is a respect formality, not gramatical rule.

Therefore, normally the rule is to put "I" **(YO) is the last**. 

Example: 

You could never say "Yo y tu sabemos", the proper way to say it is "Tu y yo"; "Yo y ellos pensamos..." the proper way is "Ellos y yo pensamos...".

If you can't say " Ellos, yo y tu sabemos.." the right way is:

"Ellos, tu y yo sabemos".