I vores kupé sad der en familie, som skulle gå om bord på det næste tog senere samme dag.

I vores kupé means in our compartment.

Danish often puts a place expression first when it sets the scene. That changes the word order of the rest of the clause, so instead of starting with the subject, the sentence starts with the location:

• I vores kupé sad der en familie ...

This is very natural in Danish and sounds a bit like English In our compartment, there was a family sitting...

Vores means our and does not change for gender or number. So you say:

• vores kupé = our compartment
• vores hus = our house
• vores bøger = our books

Unlike articles such as en/et, possessives like vores stay the same.

Both patterns exist, but here the word order follows the normal Danish V2 rule.

In main clauses, the finite verb usually comes in second position. Since I vores kupé is placed first, the verb must come next:

• I vores kupé
  • sad
    • der en familie

So:

• I vores kupé sad der en familie = correct
• I vores kupé der sad en familie = incorrect in standard Danish word order

If the sentence started with der, then you could say:

• Der sad en familie i vores kupé

That is also correct, but it has a slightly different focus.

Here der is an expletive or dummy word. It does not mean there in a literal location sense. It is used in existential-type sentences, where English often uses there is / there was.

So:

• Der sad en familie
  literally: There sat a family
• natural English: There was a family sitting

This der is very common in Danish when introducing something that exists or is present somewhere.

Danish often uses a more specific posture or position verb where English might simply use was. Here sad is the past tense of sidde, meaning sit.

So sad der en familie literally means:

• there sat a family

But in natural English, we would usually say:

• there was a family sitting
• or just there was a family

Danish frequently uses verbs like:

• sidde = sit
• stå = stand
• ligge = lie
• hænge = hang

where English may prefer a more general verb.

En familie means a family, so it introduces new information. The speaker is mentioning this family for the first time.

If it were familien, that would mean the family, as if the listener already knew which family was being referred to.

So here:

• en familie = a family, one family
• familien = the family

Som is a relative pronoun here, meaning who or that.

It connects en familie with the extra information about them:

• en familie, som skulle gå om bord ...
• a family, who/that were going to board ...

In English, who is common for people, but Danish uses som very broadly.

Not necessarily. Skulle can mean had to, but it also often means was/were going to or was/were supposed to depending on context.

Here it most naturally means:

• were going to board
• or were due to board

So:

• som skulle gå om bord på det næste tog senere samme dag

means the family was going to board the next train later that same day.

This is a very common use of skulle in Danish.

Gå om bord på means to board a form of transport.

So:

• gå om bord på toget = board the train
• gå om bord på flyet = board the plane
• gå om bord på skibet = board the ship

The phrase is made up of:

• gå = go
• om bord = on board
• på = on / onto, used with the vehicle

It is a fixed expression, so it is best learned as a whole phrase.

The preposition på is used with gå om bord when talking about the vehicle being boarded:

• gå om bord på toget
• gå om bord på bussen

Det næste tog means the next train.

So the whole part means:

• board the next train

Notice also that tog is a neuter noun, so the definite form is det:

• et tog
• toget
• det næste tog

In Danish, when an adjective comes before a definite noun, you usually need:

1. a definite determiner such as den/det/de
2. the adjective in its definite form
3. the noun usually in its indefinite form

So:

• det næste tog = the next train

Compare:

• et næste tog = incorrect
• næste toget = incorrect
• det næste toget = also incorrect in standard usage here

This is a very important Danish pattern:

• det store hus = the big house
• den gamle mand = the old man
• de røde biler = the red cars

Senere samme dag means later the same day.

The phrase samme dag means the same day. Danish often uses samme without a separate article in expressions like this:

• samme dag = the same day
• samme aften = the same evening
• samme uge = the same week

So senere samme dag is a natural fixed-type expression meaning later that same day or later the same day.

Yes, you could say:

• I vores kupé var der en familie ...

That would mean roughly There was a family in our compartment ...

The difference is that sad der en familie gives a more vivid picture: the family is specifically described as sitting there. Danish often prefers these more concrete verbs.

So:

• var der en familie = more neutral, simply states existence
• sad der en familie = more visual, tells you their position

Kupé means compartment, especially on a train.

It is a common gender noun:

• en kupé
• kupéen = the compartment

In the sentence, it appears after the possessive:

• vores kupé = our compartment

Even though modern trains often have open carriages rather than classic compartments, the word is still understood and used when appropriate.