Puer fatetur se veritatem celare et matrem paene fallere voluisse.

Because Latin often uses an accusative-and-infinitive construction instead of a separate that-clause.

After verbs of saying, thinking, knowing, perceiving, and admitting, Latin commonly does this:

• subject of the subordinate idea in the accusative
• verb of that subordinate idea in the infinitive

So here:

• fatetur = admits
• se ... voluisse = that he had wanted ...

Latin does not need a separate word meaning that here.

Se is accusative because it is the subject of the infinitive voluisse inside indirect statement.

In English, we say:

• The boy admits that he wanted...

In Latin, that becomes:

• Puer fatetur se ... voluisse

So se means himself, and here it refers back to puer.

This is a very common pattern:

• main subject: puer
• reflexive accusative subject inside indirect statement: se

So the boy is admitting something about himself.

Fatetur is a deponent verb.

Its dictionary form is fateor, fatēri, fassus sum.
Deponent verbs look passive in some forms, but they have active meanings.

So although fatetur looks passive in form, it means:

• he admits
• he confesses
• he acknowledges

It is:

• 3rd person singular
• present indicative

So puer fatetur = the boy admits / is admitting.

Voluisse is the perfect active infinitive of volo (to want).

That means it expresses having wanted.

In this sentence, it is the main infinitive of the indirect statement:

• se ... voluisse = that he had wanted ...

A very important point: in Latin indirect statement, infinitive tenses are usually relative, not absolute.

So:

• voluisse is earlier than fatetur

That is why English may translate it as:

• admits that he wanted or more literally,
• admits that he had wanted

Both can be reasonable depending on context.

Because celare and fallere depend on voluisse.

The idea is:

• he wanted to hide the truth
• and to almost deceive his mother

So:

• voluisse = to have wanted
• celare = to hide
• fallere = to deceive

The present infinitives celare and fallere are not telling you time directly from the speaker’s point of view. They show action simultaneous with the wanting.

In other words, at the time when he wanted, what did he want?
He wanted:

• to hide the truth
• and to almost deceive his mother

Because they are the direct objects of the infinitives:

• veritatem goes with celare
• matrem goes with fallere

So the structure is:

• veritatem celare = to hide the truth
• matrem fallere = to deceive his mother

Both celare and fallere take a direct object in the accusative.

Paene means almost, and here it most naturally modifies fallere.

So:

• matrem paene fallere = to almost deceive his mother

Its position right before fallere strongly suggests that connection.

That is more natural than taking it with voluisse.
If Latin wanted to emphasize almost wanted, you would expect the wording to point more clearly in that direction.

So the normal reading is:

• he wanted to hide the truth
• and almost deceive his mother

The sentence has two main parts:

1. Puer fatetur

   • the main clause
   • The boy admits

2. se veritatem celare et matrem paene fallere voluisse

   • the indirect statement
   • literally: himself to have wanted to hide the truth and almost deceive his mother

A helpful way to break the second part down is:

• se = subject of the infinitive
• voluisse = infinitive verb of the indirect statement
• veritatem celare = one thing he wanted to do
• et matrem paene fallere = another thing he wanted to do

So the whole indirect statement is built around se ... voluisse.

Latin word order is much freer than English word order.

Placing voluisse at the end is very natural because Latin often puts the key verb of a subordinate idea at or near the end. Here that also helps gather together the actions he wanted:

• veritatem celare
• et matrem paene fallere
• voluisse

So the reader/hearer first gets the content of the desire, and then the sentence closes with voluisse.

This kind of ending is very common and often sounds elegant in Latin.

Normally, no: in a sentence like this, se refers back to the subject of the main clause, which is puer.

So the default reading is:

• The boy admits that he himself had wanted...

Latin uses reflexive pronouns very consistently this way.

If the sentence meant that another person had wanted, Latin would usually use a different form, not se referring back to puer.

Because fallere in Latin normally takes a direct object in the accusative.

So:

• matrem fallere = to deceive his mother

This is one of those places where English learners simply need to memorize the verb’s construction:

• fallo
  • accusative person

Likewise:

• celo can take a direct object of the thing hidden, as in veritatem celare

So both infinitive phrases are grammatically very straightforward:

• veritatem celare
• matrem fallere

No, not at all.

Strictly speaking, voluisse is to have wanted, so in relation to fatetur it is prior in time. But English often prefers a simpler tense:

• He admits that he wanted...

That is usually perfectly good English.

If you want to show the Latin time relationship more explicitly, you could say:

• He admits that he had wanted...

So:

• wanted = good idiomatic English
• had wanted = more explicitly shows the perfect infinitive

Both may be acceptable depending on context.