Learn Hardcore Spanish (Spain): Mi hermano está aburrido cuando pierde, pero no quiero que se sienta decepcionado. - My brother is bored when he loses, but I don’t want him to feel disappointed.

If you said Mi hermano es aburrido cuando pierde, it would sound like: My brother is boring when he loses (he becomes a boring person in those situations), which is a different meaning.

Could I say Mi hermano se aburre cuando pierde instead of Mi hermano está aburrido cuando pierde?

Yes, you can, and it sounds very natural:

Mi hermano se aburre cuando pierde. = My brother gets bored / becomes bored when he loses.
Mi hermano está aburrido cuando pierde. = My brother is bored when he loses.

Nuance:

se aburre (from aburrirse) focuses more on the process or reaction: he starts to get bored when he loses.
está aburrido describes his state at that moment: he is bored then.

Both are fine in Spain; se aburre is probably even more common in everyday speech for this idea.

Why is it pierde and not perder or pierda after cuando?

The clause cuando pierde uses the present indicative (él pierde) because:

It talks about something that happens in general / habitually: when he loses (whenever that happens).
In Spanish, for general habitual actions, after cuando we normally use the present indicative, not the infinitive.

Compare:

Mi hermano está aburrido cuando pierde.
My brother is bored when he loses (in general).

You would use pierda (subjunctive) in a future or more hypothetical sense:

Estará aburrido cuando pierda.
He will be bored when he loses.

Here, pierda refers to a future event that hasn’t happened yet.

Why is it no quiero que se sienta and not no quiero que se siente?

Because quiero que… is one of the classic triggers for the present subjunctive in Spanish.

querer que + [another subject] + subjunctive

Structure here:

(Yo) no quiero = I don’t want
que = that
(él) se sienta = he feels (subjunctive, from sentirse)

se sienta is the present subjunctive, 3rd person singular of sentirse:

Indicative: él se siente
Subjunctive: él se sienta

So:

No quiero que se sienta decepcionado.
I don’t want him to feel disappointed.

If you said no quiero que se siente, that would be using the present indicative, which is ungrammatical in this structure.

What’s the difference between sentir and sentirse, and why is se sienta used here?

Sentir and sentirse are related but not the same:

sentir + noun = to feel (something)
- Siento frío. = I feel cold.
- Siento miedo. = I feel fear.
sentirse + adjective/adverb = to feel (a certain way)
- Me siento triste. = I feel sad.
- Se siente mal. = He/She feels bad.

In the sentence:

decepcionado is an adjective (disappointed), not a noun.
So Spanish uses sentirse: se sienta decepcionado = he feels disappointed.

That’s why we need the reflexive pronoun se and the verb sentirse in subjunctive: se sienta.

Why do we need que in no quiero que se sienta decepcionado?

Que here is a conjunction, not a relative pronoun. It links two different clauses:

No quiero – main clause (I don’t want)
que se sienta decepcionado – subordinate clause (that he feel disappointed)

In Spanish, when you express wanting, hoping, asking, etc. about another person’s action or state, you almost always need this que:

Quiero que vengas. – I want you to come.
Espero que estés bien. – I hope you’re well.
No quiero que se sienta decepcionado. – I don’t want him to feel disappointed.

You cannot say:

✗ No quiero se sienta decepcionado. (incorrect)

You can rephrase the idea in other ways, but the structure will change:

No quiero verlo decepcionado. – I don’t want to see him disappointed.

Why is it se sienta decepcionado and not se sienta decepcionada or decepcionados?

Adjectives in Spanish must agree in gender and number with the noun they describe.

Subject of the subordinate clause: (él) = mi hermano (masculine, singular)
So the adjective must also be masculine singular: decepcionado

Other possibilities:

If it were your sister:
No quiero que mi hermana se sienta decepcionada.
If it were your brothers (plural, at least one male):
No quiero que mis hermanos se sientan decepcionados.
If it were only sisters (all female):
No quiero que mis hermanas se sientan decepcionadas.

Why is the no placed before quiero and not before se sienta?

In Spanish, no normally goes directly before the conjugated verb it negates.

The negated idea here is “I don’t want”, not “he doesn’t feel”:

No quiero que se sienta decepcionado.
= I don’t want him to feel disappointed. (He might feel that way, but that’s not what you want.)

If you instead negated the second verb:

Quiero que no se sienta decepcionado.
Literally: I want him not to feel disappointed.

This is also grammatically correct, but the emphasis is slightly different:

No quiero que se sienta… centers on your own lack of desire.
Quiero que no se sienta… sounds more like you actively want him to avoid that state.

In everyday speech, No quiero que se sienta… is more common for this idea.

Why is pero used and not sino?

Both pero and sino can be translated as “but”, but they’re used differently:

pero = but, used for simple contrast or addition
sino = but rather / but instead, usually after a negation and to correct or replace something

In the sentence:

Mi hermano está aburrido cuando pierde, pero no quiero que se sienta decepcionado.

The first part is not negated, it’s just describing something true. Then pero introduces a contrasting idea: however, I don’t want him to feel disappointed.

Examples to see sino:

No está aburrido, sino cansado.
He’s not bored, but rather tired.

Because the first clause here is not negative, pero is the correct conjunction.

Is the comma before pero necessary in ..., pero no quiero que se sienta decepcionado?

Yes, in normal written Spanish you put a comma before pero when it connects two clauses, just as in English:

Mi hermano está aburrido cuando pierde, pero no quiero que se sienta decepcionado.

If both parts were very short, you might occasionally see it without a comma, but the standard and most correct form in writing is with the comma.