Mi abuelo cuenta la historia del origen de nuestra familia.

Contar has two main meanings:

1. To count (numbers)

   • contar hasta diez = to count to ten

2. To tell / to relate (a story)

   • contar una historia = to tell a story

In Mi abuelo cuenta la historia…, the context is clearly about a story, so contar is used in the sense of “to tell”, not “to count.”

Contar is a stem‑changing verb (o → ue) in the present tense.

Conjugation (present, indicative):

• yo cuento
• tú cuentas
• él / ella / usted cuenta
• nosotros contamos
• ustedes / ellos cuentan

The subject is mi abuelo (3rd person singular: he), so you use:

• él cuenta → mi abuelo cuenta

That’s why it’s cuenta, not conta or cuentas.

With possessive adjectives like mi, tu, su, Spanish normally does not use an article:

• mi abuelo = my grandfather
• el abuelo = the grandfather (a specific grandfather, not necessarily “mine”)

So:

• Mi abuelo cuenta… = My grandfather tells…
  If you said El abuelo cuenta…, it would mean “The grandfather tells…” and sound like you’re talking about “the grandpa” as a character, not necessarily your own.

Mi (no -s) is used with singular nouns, and mis with plural nouns:

• mi abuelo = my grandfather (one person)
• mis abuelos = my grandparents / my grandfathers (more than one)

Since abuelo is singular, you must use mi, not mis.

Both are grammatically correct, but they mean slightly different things:

• la historia = the story (specific, known to speaker/listener, or “the main/official” story)
• una historia = a story (one story among others, not specified)

Mi abuelo cuenta la historia del origen de nuestra familia suggests there is a particular, known story about your family’s origin — maybe the “official” family story everyone knows.

If you said una historia del origen de nuestra familia, it might sound like there are several possible stories and this is just one of them.

Del is the contraction of de + el:

• de = of / from
• el = the (masculine singular definite article)

origen is masculine, so you would normally say de el origen. But in Spanish de el contracts to del:

• de + el → del
• la historia del origen = the story of the origin

You must use the contracted form del; de el origen is incorrect.

• The word is spelled origen, without an accent mark. The stress falls naturally on o-RI-gen (second-to-last syllable), which follows normal Spanish stress rules for words ending in -n.
• Origen is a masculine noun:
  • el origen = the origin
  • un origen = an origin

That’s why we get del origen (= de + el origen).

Spanish possessive adjectives must agree in gender and number with the noun they modify, not with the owner.

• familia is feminine singular.
• So you use nuestra (feminine singular), not nuestro (masculine singular).

Forms of nuestro:

• nuestro libro (masc. sing.)
• nuestra casa (fem. sing.)
• nuestros libros (masc. pl.)
• nuestras casas (fem. pl.)

So:
nuestra familia = our family.

In Spanish, possessive adjectives like mi, tu, su, nuestro/a usually replace the article, they don’t appear together with la / el:

• nuestra familia = our family
• la familia = the family
  You don’t normally say la nuestra familia.

So del origen de nuestra familia is correct.
del origen de la nuestra familia is incorrect in standard Spanish.

No, that specific reordering is ungrammatical or at best very unnatural.

The usual and natural structure is:

• la historia del origen de nuestra familia
  • historia (head noun)
  • del origen (prepositional phrase modifying “historia”)
  • de nuestra familia (modifying “origen”)

If you say la historia de nuestra familia del origen, it sounds confusing, like “the story of our family of the origin,” which doesn’t match the intended meaning.

A more natural paraphrase preserving correct order would be:

• Mi abuelo cuenta la historia de cómo se originó nuestra familia.
  (My grandfather tells the story of how our family originated.)

No, decir isn’t used that way.

• decir = to say / to tell (words, phrases, messages, information)
  • Mi abuelo dice que… = My grandfather says that…
  • Mi abuelo me dice la verdad. = My grandfather tells me the truth.

But for telling a story, the natural verb is contar:

• contar una historia / un chiste / una anécdota
  = to tell a story / joke / anecdote

So:

• ✅ Mi abuelo cuenta la historia…
• ❌ Mi abuelo dice la historia… (sounds wrong to native speakers)

In Spanish, subject pronouns (yo, tú, él, etc.) are usually omitted because the verb ending already shows who the subject is.

• cuenta already indicates he / she / it / usted.
• The noun mi abuelo makes the subject completely clear.

So:

• Mi abuelo cuenta la historia… is natural and complete.
  You’d only add él for emphasis or contrast:
• Él, mi abuelo, cuenta la historia, no mi abuela.
  (HE, my grandfather, tells the story, not my grandmother.)

Spanish present tense (presente de indicativo) can express both:

1. An action happening right now

   • “My grandfather is (right now) telling the story…”

2. A habitual action (what someone usually does)

   • “My grandfather tells the story (whenever we get together).”

Without extra context, Mi abuelo cuenta la historia del origen de nuestra familia can mean either:

• He is telling it now.
• He habitually tells it (e.g., every holiday).

Context or extra words (siempre, cada año, ahora mismo, etc.) usually clarify which one is meant.