Mis suegros son muy buenos conmigo.

Suegros is the plural of:

• el suegro = father‑in‑law
• la suegra = mother‑in‑law

Mis suegros normally means “my in‑laws”, specifically my father‑ and mother‑in‑law as a couple.

You can also see los suegros used more generally, like “the in‑laws” as a category of people.

The possessive has to agree in number with the noun it modifies:

• mi suegro – my father‑in‑law (singular)
• mi suegra – my mother‑in‑law (singular)
• mis suegros – my in‑laws (plural)

So because suegros is plural, you must use mis, not mi.

Buenos agrees with suegros, not with each individual person:

• Noun: suegros → masculine plural (because suegro is masculine and a mixed group defaults to masculine in Spanish)
• Adjective: buenos → also masculine plural

Even if the actual people are one man and one woman, a mixed group takes masculine plural in Spanish:

• Mis amigos = my (male) friends or mixed group
• Mis amigas = only female friends

Likewise:

• Mis suegros son muy buenos. (father + mother‑in‑law)
• Mis suegras son muy buenas. (two mothers‑in‑law, only women)

No. Buenas is feminine plural, but suegros is masculine plural. They must match:

• ✅ Mis suegros son muy buenos conmigo.
• ✅ Mis suegras son muy buenas conmigo. (two mother‑in‑laws, all female)
• ❌ Mis suegros son muy buenas conmigo. (gender mismatch)

Here ser is used because we’re describing their character / usual way of behaving, not a temporary state.

• Ser bueno con alguien = to be a good / kind person towards someone (more permanent or typical behavior)
• Estar bueno has very different meanings (physically attractive, tasty, or in some contexts “to be well/healthy”), but not “to be kind”.

So:

• ✅ Mis suegros son muy buenos conmigo.
• ❌ Mis suegros están muy buenos conmigo. (sounds like “my in‑laws are very hot with me” or otherwise wrong)

In Spanish, when you mean “to be good/kind to someone”, the usual pattern is:

ser bueno con + person

So:
Mis suegros son muy buenos conmigo.
= My in‑laws are very good / kind to me.

Other prepositions change the meaning:

• ser bueno para mí = to be good for me (beneficial, convenient)
  • Este trabajo es muy bueno para mí. – This job is very good for me.
• ser bueno a mí ❌ is not used.

If you want to avoid conmigo, you can also say:

• Mis suegros me tratan muy bien. – My in‑laws treat me very well.
• Mis suegros son muy amables conmigo. – My in‑laws are very kind to me.

With con, Spanish uses special combined forms:

• con + mí → conmigo (with me)
• con + ti → contigo (with you, singular informal)
• con + sí → consigo (with himself/herself/themselves, in some contexts)

So con mí is incorrect; it must be:

• ✅ Mis suegros son muy buenos conmigo.
• ❌ Mis suegros son muy buenos con mí.

This is about muy vs mucho:

• muy = “very” (modifies adjectives and adverbs)
  • muy buenos = very good / very kind
• mucho / muchos / mucha / muchas = “much / many / a lot of” (modifies nouns, or used as an adverb)
  • muchos amigos = many friends
  • trabaja mucho = he works a lot

So:

• ✅ Mis suegros son muy buenos conmigo. – My in‑laws are very good to me.
• ❌ Mis suegros son muchos buenos conmigo. – Incorrect.
• ❌ Mis suegros son mucho buenos conmigo. – Incorrect.

You could say:

• Son buenos conmigo muchas veces. – They are good to me many times. (but it changes the meaning)

Yes, but the version in your sentence is the most natural:

• Neutral, standard:
  • Mis suegros son muy buenos conmigo.

Other possible orders (usually for emphasis or style):

• Conmigo, mis suegros son muy buenos.
  (Strong emphasis on “with me” → “As for me, my in‑laws are very good.”)

• Mis suegros, conmigo, son muy buenos.
  (More written or rhetorical, with commas as spoken pauses.)

But in everyday speech, the original word order is by far the most common.

Yes, a nuance difference:

• Son muy buenos conmigo.

  • Literally: “They are very good with me.”
  • Suggests their general attitude/character towards you is kind, nice, supportive.

• Me tratan muy bien.

  • Literally: “They treat me very well.”
  • Focuses more on their actions and the way they treat you (what they do).

In many contexts you can use either, but ser bueno con alguien is slightly more about what kind of people they are towards you, and tratar bien a alguien is about their behavior / treatment.

Suegros is completely neutral and widely used in all registers in Spain:

• You can say mis suegros in formal and informal situations.
• It is not slang, rude, or overly casual.

You might sometimes hear joking or informal alternatives like:

• los políticos (literally “the politicians”, a play on familia política “in‑law family”)

But suegros is the standard and safest word.

Just change conmigo to the appropriate prepositional pronoun:

• Mis suegros son muy buenos con nosotros. – …very good to us.
• Mis suegros son muy buenos con él. – …very good to him.
• Mis suegros son muy buenos con ella. – …very good to her.
• Mis suegros son muy buenos con ellos. – …very good to them (group with at least one man).
• Mis suegros son muy buenos con ellas. – …very good to them (all women).

Note: only mí (with accent) + con → conmigo is irregular. The others are regular con + pronoun.

Change suegros to the singular form and match the adjective:

• Mi suegra es muy buena conmigo. – My mother‑in‑law is very good to me.
• Mi suegro es muy bueno conmigo. – My father‑in‑law is very good to me.

Notice the agreement:

• suegra → buena (feminine singular)
• suegro → bueno (masculine singular)

Yes, some natural alternatives in Peninsular Spanish:

• Mis suegros me tratan muy bien. – My in‑laws treat me very well.
• Mis suegros son muy majos conmigo. – My in‑laws are very nice to me. (muy común en España)
• Mis suegros son muy amables conmigo. – My in‑laws are very kind to me.
• Conmigo, mis suegros se portan muy bien. – With me, my in‑laws behave very well.

All of these sound natural in Spain, with majos being particularly colloquial and common.