1) "mi", since you are talking about your brother.2) "nuestra", since you are talking about the mother of both of you - and the mother is singular, and feminine.
Cuenta
In this case it would more normally be "nuestro padre", or "our father".
Para nuestro mecánico favorito
asuntos.
Roberto es nuestro primo = Roberto is our cousin
"Our" in Spanish is nuestro, nuestra, nuestros, nuestras - depending on the gender and number of the objects that belong to you.
Nuestros amigos (for all male or a mixed male/female group). Nuestras amigas (for a female only group)
"Our" in Spanish is either "nuestro" or "nuestra", depending on whether the word after it is masculine or feminine. It is pronounced "new-ACE-trow" or "new-ACE-trah". Please see the Related link below for confirmation of the translation.
The base word for "our" in Spanish is nuestro. However this word must agree in number and gender with the item being possessed. Accordingly you must say "nuestra mesa" because mesa is feminine. Or you would say "nuestros niños" because niños is a plural word.
Alfredo Taullard has written: 'Nuestro antiguo Buenos Aires' -- subject(s): Description, History 'Cartas privadas de la familia de Rosas' 'Historia de nuestros viejos teatros' -- subject(s): Opera, Theater, Theaters
Nuestro Magazine ended in 1980.
Nuestro Magazine was created in 1977.
Nuestro Amor was created in 2006.
Nuestro Himno was created on 2006-04-28.
Padre Nuestro was created on 2007-01-22.
Nuestro ser amado. Or.. nuestro ser querido.
Nuestro Show No Puede Parar was created in 1990.