Learn Hardcore Spanish (Spain): Mi abuela me lo explicaba con paciencia y yo se lo repetía a mi hermana. - My grandmother would explain it to me patiently and I would repeat it to my sister.

Because when an indirect object pronoun le/les appears before a direct object pronoun lo/la/los/las, Spanish changes le/les to se to avoid the awkward sequence le lo. It’s a sound/structure rule, not reflexive.

Example: Le expliqué el tema a Ana → Se lo expliqué a Ana.

What order do the object pronouns have to follow?

Indirect object first, then direct object:

me/te/se/nos/os + lo/la/los/las So: me lo, se lo, not “lo me” or “lo se.” This order stays the same whether they go before a finite verb or attach to an infinitive/gerund/affirmative command.

Why is the imperfect (explicaba, repetía) used instead of the preterite?

The imperfect describes habitual, ongoing, or background actions in the past. The sentence means “used to explain” and “would repeat (habitually).”

One-time, completed events would use the preterite: Me lo explicó … Se lo repetí (she explained it to me once; I repeated it once).

Is the subject pronoun yo necessary?

No. Spanish often drops subject pronouns. Here yo is used to make the subject change crystal clear and add contrast with the first clause. Without it, …y se lo repetía a mi hermana could be ambiguous, because repetía is the same form for “I” and “she” in the imperfect.

Why add a mi hermana if se already means “to her”?

Clitic doubling of the indirect object is the norm in Spanish: use both the pronoun (se/le) and the a + person phrase.
se is ambiguous (to him/her/you-formal/them), so a mi hermana removes ambiguity and sounds natural.

Could I use para mi hermana instead of a mi hermana?

Not for the indirect object. With verbs of saying/giving/sending, Spanish uses a to mark the recipient: repetir algo a alguien.

Se lo repetía a mi hermana = I repeated it to my sister.
Se lo repetía para mi hermana = I repeated it for my sister (for her benefit), possibly to someone else.

What does lo refer to exactly, and how would it change with gender/number?

lo stands for the direct object “it,” whose gender/number matches the thing:

Feminine singular (e.g., la explicación): me la explicaba … se la repetía.
Masculine plural (e.g., los ejercicios): me los explicaba … se los repetía.
If “it” is a whole idea/statement, Spanish also uses neutral lo (invariable).

Is se reflexive here?

No. It’s the indirect object pronoun (le/les → se) meaning “to her.”
Reflexive would mean the subject acts on themself: Ella se lo repite a sí misma (“She repeats it to herself”). Here, se just marks the recipient.

Where else can these pronouns go besides before the verb?

Attached to an infinitive: Mi abuela quería explicármelo con paciencia; …quería explicárselo a mi hermana.
Attached to a gerund: Mi abuela estaba explicándomelo; …estaba explicándoselo a mi hermana. (Or place them before: Me lo estaba explicando.)
Attached to affirmative commands: Explícaselo a tu hermana.
With negative commands, they go before: No se lo expliques.

Can I move con paciencia to a different spot?

Yes, adverbials are flexible. Common options:

Mi abuela me lo explicaba con paciencia.
Con paciencia, mi abuela me lo explicaba.
Mi abuela, con paciencia, me lo explicaba. All are fine; the first is the most neutral.

What exactly can se stand for in se lo repetía?

It’s the indirect object pronoun for any of these: “to him,” “to her,” “to you (usted),” “to them,” or “to you (ustedes).” That’s why Spanish typically adds a + person for clarity: …se lo repetía a mi hermana.

Why is it mi abuela (no accent) but sometimes I see mí with an accent?

mi without an accent is the possessive adjective: mi abuela (“my grandmother”).
mí with an accent is the prepositional pronoun meaning “me”: a mí, para mí.
You could say Me lo explicaba a mí to emphasize “to me.”

Does leísmo (Spain) affect this sentence?

Not here. In standard Spanish (including most of Spain), the direct object “it” must be lo/la/los/las, so se lo is correct.

Leísmo (using le as a direct object for masculine people) does not apply because the direct object is a thing (“it”), not a person.
Also avoid laísmo/loísmo (using la/lo as indirect objects). For “to my sister,” the standard indirect object is le → se before lo.