otouto ha yasai wo taberuno wo iyagaru node, haha ha suupu ni irete dasimasu.

Here の turns the verb phrase 野菜を食べる into a noun-like unit.

• 野菜を食べる = to eat vegetables
• 野菜を食べるの = the act of eating vegetables

That lets the whole phrase become the thing that is disliked:

• 野菜を食べるのを嫌がる = to dislike / resist eating vegetables

This の is called a nominalizer. In many cases, こと can also nominalize a verb, but の is very common in everyday speech, especially for concrete actions.

They belong to different parts of the sentence.

1. 野菜を食べる

   • 野菜を marks vegetables as the object of eat

2. 食べるのを嫌がる

   • 食べるのを marks the act of eating as the object of 嫌がる

So the structure is:

• [野菜を食べる] のを 嫌がる
• [eating vegetables] is what he resists/dislikes

This can feel strange in English because Japanese allows one object phrase to contain another.

嫌がる is very natural here because it often means to act as if one dislikes something, to show reluctance, or to resist doing something.

That fits a child well:

• he does not just have a general opinion
• he visibly resists eating vegetables

Comparison:

• 嫌いだ = to dislike; describes a state or preference
  
  • 弟は野菜が嫌いだ = My younger brother dislikes vegetables
• 嫌う = to dislike/avoid; more formal or less common in casual speech for this kind of situation
• 嫌がる = to show dislike, to resist, to be unwilling

Also, 嫌がる is especially common when talking about another person’s outward behavior, since Japanese often avoids stating someone else’s internal feelings too directly.

Because 嫌がる takes the thing being disliked or resisted as its object, so を is used.

• 食べるのを嫌がる = to resist/dislike eating

By contrast, with 嫌いだ, you often see が:

• 野菜を食べるのが嫌いだ = to dislike eating vegetables

So:

• 嫌がる → often uses を
• 嫌いだ → often uses が

That difference comes from the grammar of the predicate being used.

Both ので and から can mean because, but ので usually sounds a bit softer, more explanatory, and a little more objective.

• 嫌がるので = because he resists it / since he doesn’t want to eat it

Compared with から:

• から can sound more direct or more like the speaker’s personal reasoning
• ので often sounds gentler and more descriptive

In this sentence, ので fits well because the speaker is calmly explaining why the mother serves vegetables that way.

It is a sequence of two actions joined by the て-form:

1. スープに入れて = putting it into soup
2. 出します = serves it / brings it out

So the mother:

• puts the vegetables into soup
• then serves it

In this context, 出す means to serve food or to put food on the table, not just to take out.

The object is omitted after 入れて, but it is understood to be the vegetables.

に marks the destination or place something goes into.

• スープに入れる = to put into soup

Here スープ is the container/resulting location.

Similar examples:

• 箱に入れる = put into a box
• コーヒーに砂糖を入れる = put sugar into coffee

So に is natural because something is being placed into the soup.

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

The sentence is then saying something about him:

• 弟は ... 嫌がるので
• As for my younger brother, since he resists eating vegetables...

This sets up the background for the rest of the sentence.

If が were used instead, it would sound more like identifying him specifically as the one who resists eating vegetables. But here, は is the natural choice because he is the established topic.

Yes. The object is omitted because it is obvious from context.

Earlier, the sentence talks about 野菜. So in:

• 母はスープに入れて出します

the understood meaning is:

• 母は野菜をスープに入れて出します
• The mother puts the vegetables into soup and serves it

Japanese often leaves out words that are clear from context.

Because repeating 野菜を would be grammatically fine but less natural if the listener already understands it.

Japanese frequently omits:

• subjects
• objects
• other information already established in context

So the sentence sounds smooth and natural by leaving the object understood.

In a sentence like this, 弟 normally means my younger brother unless context says otherwise.

Japanese often omits possessives like my when they are obvious.

So:

• 弟 = my younger brother
• 母 = my mother

In English, you usually need my, but in Japanese it is often left unstated.