otouto ha ongaku no onryou wo agesugita node, haha ni rimokon wo toraremasita.

は marks 弟 as the topic: As for my younger brother...

In this sentence, the speaker is setting up 弟 as the thing being talked about first:

弟は 音楽の音量を上げすぎたので、母にリモコンを取られました。

This feels like:

• As for my younger brother, he turned the music up too much, so his mother took the remote from him.

If you used が, it would sound more like you are identifying him specifically as the one who did it:

• 弟が ... = It was my younger brother who...

Both can be possible in some contexts, but は is very natural when introducing the situation as the topic.

Japanese often leaves out my, your, his, etc. when the relationship is clear from context.

So 弟 can mean:

• my younger brother
• someone’s younger brother

depending on context.

In a normal sentence like this, if the speaker says 弟, it usually means my younger brother unless something else is specified.

The same is true for 母:

• 母 usually means my mother in this kind of context.

Japanese relies heavily on context, so words like my are often unnecessary.

音楽の音量 means the volume of the music.

Breakdown:

• 音楽 = music
• 音量 = volume
• の connects nouns

So A の B often means:

• B of A
• A’s B
• B related to A

Here:

• 音楽の音量 = the music’s volume / the volume of the music

It sounds more specific than just 音量.
The speaker is not talking about volume in general, but specifically the volume of the music.

Because 音量 is the direct object of 上げすぎた.

The verb part 上げる means to raise.
What was raised? 音量.

So:

• 音量を上げる = to raise the volume

The particle を marks the thing directly affected by the action.

上げすぎた is made from:

• 上げる = to raise
• すぎる = to do too much / to exceed
• past tense た

So:

• 上げる → raise
• 上げすぎる → raise too much
• 上げすぎた → raised too much

This pattern is very common in Japanese:

• 食べすぎる = eat too much
• 飲みすぎる = drink too much
• 話しすぎる = talk too much

So 音量を上げすぎた means:

• turned the volume up too much
• raised the volume too much

ので means because / since, and it often sounds a bit more explanatory, objective, or softer than から.

So:

• 上げすぎたので = because he turned it up too much
• 上げすぎたから would also be possible, but can sound a little more direct or blunt.

Very roughly:

• ので = more neutral, explanatory
• から = more straightforward, sometimes more personal/assertive

In this sentence, ので fits naturally because the first clause gives the reason for what happened next.

Here, に marks the agent in a passive sentence.

The ending 取られました is passive, so 母に means:

• by mother
• from mother’s action

So:

• 母に リモコンを取られました = had the remote taken by my mother

In passive sentences, the person who performs the action is often marked with に.

Great question. This is one of the most important points in the sentence.

取られました is the passive form of 取る:

• 取る = to take
• 取られる = to be taken
• 取られました = was taken / had taken

But this is not just a plain passive. It is the kind of passive Japanese often uses when someone is affected in an unpleasant or inconvenient way. This is sometimes called the adversity passive or suffering passive.

So:

• 母がリモコンを取りました = Mother took the remote.

This simply states the action.

But:

• 母にリモコンを取られました = I/he had the remote taken by mother.

This highlights the person affected by the action, often with a feeling like:

• and that was annoying / unfortunate / inconvenient

That nuance is very natural here, because the brother turned the volume up too much, and as a result the mother took the remote away.

It is understood from context that the affected person is 弟.

So the structure is basically:

• 弟は ... 母にリモコンを取られました
• As for my younger brother, ... he had the remote taken by his mother.

Japanese often omits things that are obvious from context.
Even though there is no explicit word like he before 取られました, the topic 弟は carries through the sentence.

取る directly takes リモコン as its object:

• リモコンを取る = take the remote

So in the passive:

• リモコンを取られる = have the remote taken

You do not need から here because the remote itself is the thing being taken.

Also, 取ってもらいました would mean something completely different:

• 母にリモコンを取ってもらいました = I had my mother get/take the remote for me
  This usually suggests the action was done as a favor.

That is the opposite of the meaning here.
In your sentence, the mother taking the remote is not a favor—it is something done to stop the brother.

This is a very common pattern in Japanese.

Only the final verb of the sentence usually carries the main politeness level. Earlier clauses are often left in plain form, even in polite speech.

So:

• 上げすぎたので = plain past + ので
• 取られました = polite past

This is perfectly normal.

You could think of it like this:

• the non-final clause is just linking information
• the final verb sets the sentence’s overall politeness

So this sentence is grammatically and stylistically natural.

Not exactly.

取る can mean take, and in some contexts a passive form can sound like had something taken, which may feel similar to was stolen. But here the context is clearly not theft.

Because the agent is 母に and the earlier clause explains the reason, the meaning is:

• his mother took the remote away from him

So it is better understood as:

• had the remote taken away by his mother rather than
• the remote was stolen

Yes. That is a very natural English translation.

Japanese often uses the passive in places where English would prefer an active sentence. If you translated it too literally, you might get:

• My younger brother turned the music volume up too much, so he had the remote taken by his mother.

That is understandable, but it sounds awkward in English.

A smoother English version is:

• My younger brother turned the music up too much, so my mother took the remote away from him.

This captures the meaning well, even though the grammar is not a word-for-word match.