Do you remember the possesive pronouns mano, tavo, jo, jos, mūsų, jūsų, jų which are the genitive case of aš, tu, jis, ji, mes, jūs, jie, jos?

Jis yra mano brolis. (He is my brother.)
Ji yra tavo sesė. (She is your your sister.)
Latviai yra mūsų draugai. (Latvians are our friends).

When you want to express a relationship of the subject with objects that the subject possesses, you use the possesive pronoun savo:

Jis skambina savo broliui. He is calling his (own) brother.
Jis skambina savo sesei. He is calling his (own) sister.
Ji skambina savo sesei. She is calling her (own) sister.
Mes skambiname savo tėvams. We are calling our (own) parents.

Mano brolis laukia savo draugo. My brother is waiting for his friend.
Aš nekenčiu savo mokytojo. I hate my teacher.
Ar tu lauki savo dėstytojo? Are you waiting for your lecturer?

Tavo draugas man duoda savo kompiuterį. Your friend gives me his computer.
Jūsų mama gauna savo televizorių. Your mother is getting her TV.

The pronoun savo is not applicable to nouns which are not subjects:

Man patinka mano mašina. I like my car.
Tavo draugui patinka jo mašina. Your friend likes his car.