Cuando veo a mi hermano, lo abrazo.

Because cuando here is a conjunction, meaning when in a connecting sense: When I see my brother, I hug him.

With an accent mark, cuándo is usually used in questions or indirect questions, such as:

• ¿Cuándo viene? = When is he coming?
• No sé cuándo viene. = I don’t know when he’s coming.

So in this sentence, cuando without the accent is correct.

Spanish often uses the present tense for habitual actions or general truths.

So Cuando veo a mi hermano, lo abrazo means something like:

• When(ever) I see my brother, I hug him
• Whenever I see my brother, I hug him

It is not describing one single event right now. It describes a usual pattern.

In this kind of sentence, it often feels closer to whenever in English.

So although the Spanish word is cuando, the overall sense is:

• Whenever I see my brother, I hug him

English can use either when or whenever here, depending on style. Spanish does not need a separate word in this sentence.

That is the personal a.

In Spanish, when the direct object is a specific person (or sometimes a pet or personified thing), you usually put a before it.

So:

• Veo a mi hermano = I see my brother

But with things, you normally do not use this a:

• Veo la casa = I see the house

This is one of the most important differences from English, because English does not do this.

Because my brother is the one receiving the action of seeing.

Ask yourself: Whom do I see?
Answer: my brother

That makes mi hermano the direct object of veo.

The a does not make it an indirect object here. It is still a direct object; the a is just the personal a.

Lo is a direct object pronoun meaning him or it.

In lo abrazo, lo stands for a mi hermano:

• Lo abrazo = I hug him

Spanish often uses object pronouns instead of repeating the noun again and again. So instead of saying:

• Cuando veo a mi hermano, abrazo a mi hermano

you normally say:

• Cuando veo a mi hermano, lo abrazo

That sounds much more natural.

In standard Spanish grammar, lo is the normal direct object pronoun for a singular masculine person or thing:

• Veo a mi hermano → lo veo
• Abrazo a mi hermano → lo abrazo

Le is normally the indirect object pronoun:

• Le doy un regalo = I give him a present

However, in much of Spain, you may hear le used for a male person as a direct object. This is called leísmo. Even so, lo abrazo is completely standard and is the safest form for learners.

Because Spanish often drops subject pronouns when the verb form already shows who the subject is.

• veo = I see
• abrazo = I hug

So yo is unnecessary unless you want emphasis, contrast, or clarity.

For example:

• Cuando veo a mi hermano, lo abrazo. = normal
• Cuando yo veo a mi hermano, lo abrazo. = more emphatic, and usually unnecessary here

Because of the sentence structure.

Here, abrazo comes after the object pronoun lo, so it functions as a verb:

• lo abrazo = I hug him

It is the first-person singular present of abrazar.

It is true that abrazo can also be a noun:

• un abrazo = a hug

But in this sentence, the grammar clearly shows it is a verb, not a noun.

Not naturally in this exact form. This sentence most naturally describes a habitual action.

If you want to talk about a future situation, Spanish usually changes the verb after cuando:

• Cuando vea a mi hermano, lo abrazaré. = When I see my brother, I’ll hug him.

So:

• Cuando veo a mi hermano, lo abrazo = habitual / whenever
• Cuando vea a mi hermano, lo abrazaré = future event

This is a very common difference between English and Spanish.

The comma is very natural and standard here because the sentence begins with a subordinate clause:

• Cuando veo a mi hermano, lo abrazo.

In Spanish, when a clause like cuando veo a mi hermano comes first, a comma is commonly used before the main clause.

If you reverse the order, the comma is usually not needed:

• Lo abrazo cuando veo a mi hermano.

Yes, absolutely.

That means:

• When(ever) I see him, I hug him

Here, lo replaces a mi hermano in the first clause as well:

• Cuando lo veo = When I see him
• lo abrazo = I hug him

This is very natural if it is already clear who him refers to. The original sentence mentions mi hermano explicitly first, which is helpful when introducing the person.