sono kodomo ha haha ni sokkuri desu.

Because そっくり commonly takes に to mark the person or thing someone resembles.

The pattern is:

A は B に そっくりです。
= A is exactly like / looks just like B.

So in this sentence:

• その子供は = as for that child
• 母に = to the mother / like the mother
• そっくりです = is the spitting image / looks exactly alike

The に here does not mean a destination like to in English. It is just the particle used with そっくり.

そっくり means exactly alike, very similar, or the spitting image of.

In this sentence, it usually refers to appearance, so the idea is:

• the child looks just like the mother
• the child strongly resembles the mother

A useful thing to know is that そっくり can also be used in other ways in Japanese, but in this pattern it means to resemble closely.

Examples:

• 父にそっくりです。 = He looks just like his father.
• 姉にそっくりです。 = She looks just like her older sister.

Yes, in this sentence そっくり works like an adjectival predicate.

Japanese learners often wonder where the verb look or resemble is, because English needs one. Japanese does not need a separate verb here. そっくり itself carries the idea of strong resemblance, and です makes the sentence polite.

So:

• そっくりだ = plain form
• そっくりです = polite form

That is why the sentence can end naturally with です.

This is a very common question.

母 is a plain word for mother, and it is often used when referring to one’s own mother in a neutral or somewhat formal way.

お母さん is often used:

• when addressing your mother directly
• when referring to someone else’s mother
• in more everyday family-style speech

In this sentence, 母 sounds more neutral or textbook-like. It can be understood as the mother or his/her mother, depending on context.

Very natural alternatives could include:

• その子供は母親にそっくりです。
• その子はお母さんにそっくりです。

The exact choice depends on style and context.

In this sentence, it is understood as the child’s mother.

Japanese often leaves relationships implicit when context makes them obvious. Since the sentence is about that child, the natural interpretation is:

That child looks just like his/her mother.

English often needs his or her, but Japanese usually does not. The relationship is understood from context.

は marks the topic of the sentence.

So その子供は means:

• as for that child
• speaking of that child

The sentence is not just identifying the child; it is making a comment about the child. The comment is:

母にそっくりです = looks just like the mother

So the structure is:

• topic: その子供は
• comment: 母にそっくりです

Both can be possible, but they mean slightly different things.

• その子供 refers to a child near the listener, or a child already mentioned in the conversation
• あの子供 refers to a child that is away from both speaker and listener, or something both can identify as that one over there

So the choice between その and あの depends on context.

Very roughly:

• その = that (near you / already mentioned)
• あの = that (over there)

Yes.

You may see:

• 子供
• 子ども
• こども

All are used.

The reading is the same: こども.

The differences are mostly about writing style, publishing preferences, or formality. In many textbooks, 子供 is common and easy to recognize.

No. Normal Japanese writing does not usually use spaces between words.

The standard writing would be:

その子供は母にそっくりです。

Spaces are often added in beginner materials to help learners see the parts of the sentence more easily.

Yes, in English there usually would be.

Japanese often omits possessives like his, her, their, or the child’s when the meaning is clear from context. So 母 by itself can be understood as:

• his mother
• her mother
• the mother

Here, because the sentence is about the child, the natural English meaning is:

That child looks just like his/her mother.

Not only physical appearance, but that is the most common meaning in a sentence like this.

Depending on context, そっくり can also mean someone resembles another person in:

• voice
• personality
• facial expression
• behavior

But if nothing else is specified, most people will first think of appearance.

Yes, absolutely.

その子 is often more natural in everyday speech than その子供.

Compare:

• その子供は母にそっくりです。 = slightly more explicit, possibly more textbook-like
• その子は母にそっくりです。 = very natural, conversational

Both are grammatically correct.

The plain-form version is:

その子供は母にそっくりだ。

The original sentence ends with です, which makes it polite:

• そっくりです = polite
• そっくりだ = plain

So the difference is not in meaning, but in level of politeness.