Learn Croatian: Brat se javio jučer. - My brother got in touch yesterday.

In Croatian, possessive pronouns like moj (my) are frequently left out when talking about close family members or body parts. Since it is obvious from the context that you are talking about your own brother, you do not need to include it.

What is the word se doing in this sentence?

It changes the meaning of the verb. The base verb javiti means to report or inform. When you add the reflexive pronoun se, it becomes javiti se, which is a set phrase meaning to get in touch, reach out, or answer the phone.

Where is the helper verb for the past tense? Shouldn't it be 'Brat se je javio'?

You have a great eye! The past tense normally requires the helper verb je for the third person singular. However, there is a special rule in Croatian: whenever je ends up next to the reflexive pronoun se, the je is dropped entirely.

Why does se come right after Brat?

The word se is an enclitic, which is a small, unstressed word. Croatian grammar has a strict rule that enclitics almost always go in the second position in a sentence. Because Brat is the first word, se naturally claims the second spot.