Learn Hardcore Spanish (Spain): No quiero mentir a mi familia, sino decir la verdad. - I do not want to lie to my family, but rather tell the truth.

You would not normally say quiero no mentir, because that sounds more like “I want not to lie” (a slightly different focus). The natural, neutral way is no quiero + infinitive.

What is the difference between pero and sino, and why is sino used here?

Both pero and sino can be translated as but, but they are used in different situations.

pero = “but” (adds a contrast or an exception)
sino = “but rather / but instead” (corrects or replaces something after a negation)

We use sino after a negative statement when we want to correct or replace part of it:

No quiero mentir a mi familia, sino decir la verdad.
I don’t want to lie to my family, but rather tell the truth.
→ “Lying” is rejected and replaced with “telling the truth.”

Compare with pero:

Quiero mentir a mi familia, pero me siento mal.
I want to lie to my family, but I feel bad.
→ No direct replacement, just an additional contrast.

So here, because the first part is negative (No quiero…) and the second part corrects what is wanted (not lie, but tell the truth instead), sino is the correct conjunction.

Could I say No quiero mentir a mi familia, pero quiero decir la verdad instead?

Yes, that sentence is grammatically correct and understandable:

No quiero mentir a mi familia, pero quiero decir la verdad.

However, it is:

longer (you repeat quiero unnecessarily),
slightly less sharp and elegant than using sino.

Native speakers prefer the shorter, more natural correction structure with sino:

No quiero mentir a mi familia, sino decir la verdad.

Both versions express almost the same idea, but sino is the more idiomatic choice in this specific “not X, but rather Y” pattern.

Why are mentir and decir in the infinitive, and not conjugated like miento or digo?

Two things are going on:

Verb after querer
In Spanish, when two verbs share the same subject, the second verb is usually in the infinitive:
- (Yo) quiero mentir. – I want to lie.
- (Yo) quiero decir la verdad. – I want to tell the truth.
So quiero mentir and quiero decir are the normal structures.
Omission of the repeated verb after sino
Logically, the full structure would be:
- No quiero mentir a mi familia, sino (quiero) decir la verdad.
But in Spanish you don’t normally repeat quiero here, because it is clear from context. You just keep the infinitive:
- No quiero mentir a mi familia, sino decir la verdad.

So mentir and decir are infinitives because:

they depend on quiero, and
the second quiero is understood and omitted.

Why is it mentir a mi familia and not mentir mi familia?

The verb mentir works like “to lie to someone”, not “to lie someone”:

mentir a alguien = to lie to someone

Because the object is a person (or people), Spanish uses the “personal a”:

a mi familia (to my family)

So:

No quiero mentir a mi familia.
I don’t want to lie to my family.

Saying mentir mi familia would be ungrammatical; Spanish needs the preposition a before the indirect object mi familia.

Can I use a pronoun instead of a mi familia, like No quiero mentirles?

Yes, you can. There are several natural options:

Using only a pronoun (family seen as plural people):
- No les quiero mentir.
- No quiero mentirles.
→ les refers to “them” (my family members).
Using only the noun:
- No quiero mentir a mi familia.
Using both (common in spoken Spanish, called “clitic doubling”):
- No les quiero mentir a mi familia.
  (I don’t want to lie to them, to my family.)

About number and gender:

Grammatically, familia is singular, so the standard singular pronoun would be le:
No quiero mentirle a mi familia.
But many speakers conceptualize mi familia as the group of individual people, so they say les to match that idea:
No les quiero mentir a mi familia.

Both patterns are heard, especially in everyday speech.

Why is there a comma before sino? Is it required?

The comma before sino in:

No quiero mentir a mi familia, sino decir la verdad.

is standard and recommended because:

sino is joining two contrasted elements,
the comma helps separate the two parts clearly, much like the comma before but often does in English.

In many cases, Spanish requires a comma before conjunctions like sino, pero, aunque, especially when they connect longer clauses. Here:

Including the comma is the norm and looks correct.
Omitting it (No quiero mentir a mi familia sino decir la verdad) is sometimes seen in casual writing but is less standard.

Why do we say decir la verdad and not just decir verdad?

In Spanish, abstract nouns often take the definite article el / la when they refer to a general concept:

la verdad = (the) truth (in general)
la libertad = freedom
el amor = love

So the natural, idiomatic phrase is:

decir la verdad – to tell the truth

Without the article:

decir verdad sounds incomplete or old-fashioned; it’s not how people normally speak today.

There is a fixed expression es verdad (it’s true) without an article, but in this decir + noun pattern, you want la verdad.

Could I say sino que decir la verdad instead of sino decir la verdad?

No, not in this sentence. The difference is:

sino + infinitive / noun / phrase
sino que + conjugated verb (a full clause)

Examples:

No quiero mentir, sino decir la verdad.
(infinitive after sino)
No quiero mentir, sino que quiero decir la verdad.
(full clause after sino que)

So:

sino decir la verdad ✅
sino que decir la verdad ❌ (incorrect, because decir is not conjugated here)

If you want to use sino que, you need a conjugated verb:

No quiero mentir a mi familia, sino que quiero decir la verdad.

What tense and person is quiero, and how would I say “I wouldn’t want to lie to my family, but rather tell the truth”?

quiero is:

1st person singular (yo)
Present indicative of querer

So No quiero… = I don’t want…

To say “I wouldn’t want to lie to my family, but rather tell the truth”, you can use:

No querría mentir a mi familia, sino decir la verdad.
No quisiera mentir a mi familia, sino decir la verdad.

Both querría and quisiera (imperfect subjunctive used politely) can express a softer, more hypothetical “wouldn’t want” in Spanish.

Why isn’t the subject yo written in No quiero mentir a mi familia…?

Spanish is a “pro-drop” language: subject pronouns (yo, tú, él…) are often omitted because the verb ending already shows who the subject is.

quiero can only be yo (I) in this context,
so No quiero mentir a mi familia… is completely clear without yo.

You could say:

Yo no quiero mentir a mi familia, sino decir la verdad.

This is still correct, but it usually adds emphasis on yo (“I don’t want to lie…”). In neutral statements, Spanish speakers usually drop yo.

If I reverse the ideas and say No quiero decir la verdad, sino mentir a mi familia, is that still correct?

Yes, grammatically it is correct:

No quiero decir la verdad, sino mentir a mi familia.

But now the meaning is the opposite:

Original: No quiero mentir…, sino decir la verdad.
→ I reject lying and choose telling the truth.
Reversed: No quiero decir la verdad, sino mentir….
→ I reject telling the truth and choose lying.

So the structure with sino stays correct in both, but be aware that switching the two infinitives completely changes what you are saying.