Learn Hardcore Spanish (Latin America): Estoy muy agradecido por el apoyo de mi familia. - I am very grateful for my family's support.

Spanish normally uses estar with emotional or mental states that are seen as conditions, not as permanent traits. Being (currently) grateful is treated like being happy, sad, tired, etc.

Estoy muy agradecido ≈ “I’m (feeling) very grateful right now / in this situation.”
Soy muy agradecido would mean “I’m a very grateful person (by nature, as a lasting characteristic),” which is much less common and sounds a bit odd if you just mean gratitude for a specific thing.

So, in this sentence, estoy is the natural choice because you’re talking about gratitude in response to your family’s support, not your permanent personality.

Why is it agradecido and not agradecida?

The adjective agradecido has to agree in gender and number with the person who is speaking (the subject yo).

If the speaker is male:
Estoy muy agradecido por el apoyo de mi familia.
If the speaker is female:
Estoy muy agradecida por el apoyo de mi familia.

For plurals:

A group of only men (or mixed men & women):
Estamos muy agradecidos por el apoyo de nuestra familia.
A group of only women:
Estamos muy agradecidas por el apoyo de nuestra familia.

So you choose -o or -a (and -os / -as for plurals) to match the speaker(s).

Why is it muy agradecido and not mucho agradecido?

In Spanish:

muy modifies adjectives and adverbs:
- muy agradecido (very grateful)
- muy cansado (very tired)
- muy bien (very well)
mucho modifies nouns and verbs:
- mucho apoyo (a lot of support)
- mucho dinero (a lot of money)
- Te agradezco mucho. (I thank you a lot.)

Since agradecido is an adjective, you must use muy.
Estoy mucho agradecido is incorrect in standard Spanish.

Why do we say por el apoyo and not para el apoyo?

Here por expresses the reason / cause for the gratitude:

agradecido por el apoyo ≈ “grateful because of the support / for the support”

Very roughly:

por → “because of, due to”
para → “for the purpose of, in order to, destined for”

So para el apoyo would sound like you’re talking about a purpose: “for the support” in the sense of “in order to support,” which is not the intended meaning here.

With agradecido, the natural preposition for the thing you are grateful about is por:

Estoy agradecido por tu ayuda.
Estamos agradecidos por todo.

Could I say Estoy muy agradecido a mi familia instead? What’s the difference?

Yes, and the nuance changes slightly:

Estoy muy agradecido por el apoyo de mi familia.
Focuses on what you’re grateful for (the support).
Estoy muy agradecido a mi familia.
Focuses on who you’re grateful to (your family).

You can also combine both ideas:

Estoy muy agradecido a mi familia por su apoyo.
“I’m very grateful to my family for their support.”

All three are grammatically correct; the original just highlights the support as the main focus.

Why is it el apoyo and not just apoyo with no article?

In Spanish, when you talk about a specific instance of an abstract noun, you usually use the definite article:

por el apoyo de mi familia = for the support (that) my family (has given me)

Without context, por apoyo would sound very odd here. Nouns like apoyo, amor, respeto, ayuda often take el / la / los / las when you’re referring to a particular, concrete case:

Gracias por la ayuda. (Thanks for the help.)
Aprecio mucho el apoyo. (I really appreciate the support.)

You could also say, more personally:

por su apoyo (for their support)
por todo el apoyo (for all the support)

Why is it mi familia and not mis familia, if “family” is many people?

In Spanish, familia is grammatically singular, even though it refers to a group. The possessive matches the grammar, not the real-world number of people:

mi familia (my family – one family, singular noun)
mis familias (my families – more than one family, plural noun)

So:

mi familia = correct
mis familia = incorrect (you’d be mixing plural mis with singular familia)

If I’m a woman, do I have to change the whole sentence?

You only need to change the adjective’s ending; everything else stays the same:

Male speaker: Estoy muy agradecido por el apoyo de mi familia.
Female speaker: Estoy muy agradecida por el apoyo de mi familia.

The verb estoy, the adverb muy, and the rest of the phrase por el apoyo de mi familia do not change with the speaker’s gender.

Can I omit muy and just say Estoy agradecido por el apoyo de mi familia?

Yes, that’s perfectly correct:

Estoy agradecido por el apoyo de mi familia.

The difference is only in intensity:

agradecido = grateful
muy agradecido = very grateful

So muy is optional emphasis, just like in English.

Is agradecido por the only option, or can I use other prepositions?

You’ll see three main patterns:

agradecido por + thing (reason)
- Estoy agradecido por el apoyo de mi familia.
agradecido a + person (recipient)
- Estoy agradecido a mi familia.
In much of Latin America, also agradecido con + person
- Estoy muy agradecido con mi familia.
  (very common in Mexico, Colombia, and other countries)

So, for Latin American usage, these are all natural:

Estoy muy agradecido por el apoyo de mi familia.
Estoy muy agradecido a mi familia por su apoyo.
Estoy muy agradecido con mi familia por su apoyo.

Could I just say Gracias por el apoyo de mi familia instead?

You can, but it changes who you’re thanking.

Gracias por el apoyo de mi familia.
Literally: “Thank you for the support of my family.”
This sounds like you’re thanking someone else for having supported your family.

The original sentence:

Estoy muy agradecido por el apoyo de mi familia.
Means that your family has supported you, and you’re grateful for that.

If you want to use gracias with the same meaning, you’d normally say:

Estoy muy agradecido por el apoyo de mi familia.
(as given)
or: Le(s) doy las gracias a mi familia por su apoyo.
“I thank my family for their support.”

How can I use this structure in other sentences?

You can reuse the pattern:

Estar + (muy) agradecido/a + por + [thing]

Examples:

Estoy muy agradecido por tu ayuda.
I’m very grateful for your help.
Estamos agradecidos por esta oportunidad.
We’re grateful for this opportunity.
Estaré muy agradecida por cualquier información.
(female speaker) I’ll be very grateful for any information.

Just remember to:

Conjugate estar (estoy, estás, está, estamos...),
Match agradecido / agradecida / agradecidos / agradecidas with the speaker(s),
Use por for the thing you’re grateful for.