Tengo dos hermanos.
English: I have two brothers.
In Spanish, cardinal numbers (numerales cardinales) are used to count things (one, two, three...), and ordinal numbers (numerales ordinales) are used to show order (first, second, third...).
Use cardinal numbers to count objects, people, or things. Use ordinal numbers to talk about the position or order of something (like 'the first day', 'the second floor').
Tengo dos hermanos.
English: I have two brothers.
Vivo en el tercer piso.
English: I live on the third floor.
Hay cinco libros en la mesa.
English: There are five books on the table.
Es mi primer coche.
English: It's my first car.