Apparently you are asking this so you know whether to tú/vosotros/vosotras (familiar form) or usted(Ud./Vd.)/ ustedes (Uds./Vds.) in Spanish? When in doubt, it's best to use the formal form in Spanish.
If you are on a first-name basis with someone, that is an indication that you may use the familiar form. This would apply to someone your age and/or younger. If it is someone older, a "servant/domestic/employee" it's best to use the formal, or at least to ask the person. For members of the family, including family pets, use the familiar form. But don't be surprised when you hear a native Spanish speaker using the formal with parents, as a sign of respect. A parent may switch from the familiar to the formal when angry! There will be individual differences.
In the United States, people do not distinguish between familiar and/or formal with "you." (Rarely will you hear "thee/thou.") if you hear expressions such as "you/youse guys" that is sub-standard English. In the South you are apt to hear "you-all" but that's a regionalism, and considered impolite!