Mine søskende sparer op til deres egen lejlighed i byen.

Because søskende is plural here, so Danish uses the plural possessive mine.

• min = my (common gender singular)
• mit = my (neuter singular)
• mine = my (plural)

So:

• min bror = my brother
• mit barn = my child
• mine søskende = my siblings

Søskende can refer to siblings in general, and in many contexts it is understood as plural. In this sentence, it clearly means more than one sibling because it goes with:

• mine = my (plural)
• sparer = are saving
• deres = their

If you want to refer to just one sibling, Danish usually says:

• en søster = a sister
• en bror = a brother
• or sometimes et søskendebarn means something else entirely, so it should not be confused

A single sibling is often expressed less directly in everyday Danish than in English.

At spare op means to save up.

It is a very common verb combination:

• spare = save
• spare op = save up, put money aside over time for something

Examples:

• Jeg sparer op. = I am saving up.
• Vi sparer op til en bil. = We are saving up for a car.

So in your sentence, sparer op suggests a goal they are working toward financially.

Because Danish usually says spare op til noget = save up for something.

So:

• sparer op til deres egen lejlighed = are saving up for their own apartment

This works much like English save up for.

Examples:

• Han sparer op til en ferie. = He is saving up for a holiday.
• De sparer op til et hus. = They are saving up for a house.

Because the owner is plural: mine søskende = my siblings.

Danish uses:

• sin / sit / sine for his/her/its own when the possessor is singular and refers back to the subject
• deres for their

So:

• Han elsker sin hund. = He loves his own dog.
• Hun fandt sit pas. = She found her own passport.
• De elsker deres hund. = They love their dog.
• Mine søskende sparer op til deres egen lejlighed. = My siblings are saving up for their own apartment.

Since the subject is plural, sin cannot be used here.

Egen means own.

So:

• deres lejlighed = their apartment
• deres egen lejlighed = their own apartment

It adds emphasis: the apartment belongs to them, not to someone else, and it may suggest independence.

Egen changes form depending on grammar:

• egen (common gender singular)
• eget (neuter singular)
• egne (plural or definite contexts)

Because lejlighed is a common gender singular noun, the form is egen.

Because after til in this kind of sentence, Danish often uses the noun in an indefinite form when speaking generally about a goal.

• til deres egen lejlighed = for their own apartment

This sounds natural when the focus is on the idea of obtaining an apartment, not on one already established apartment.

If you said lejligheden, it would sound like a specific apartment already known from the context:

• De sparer op til lejligheden i byen. = They are saving up for the apartment in the city.

That is more specific.

It is singular because the idea is that they are saving up for one apartment.

• deres egen lejlighed = their own apartment

Even though my siblings is plural, the sentence suggests they are saving for one shared apartment. If you wanted to say each of them is saving for separate apartments, you would need a different phrasing, for example:

• Mine søskende sparer op til hver deres lejlighed i byen.

That means something like My siblings are each saving up for their own apartment in the city.

I byen literally means in the city / in town.

In this sentence, it describes where the apartment is:

• en lejlighed i byen = an apartment in the city / in town

Depending on context, English could translate it either way:

• in the city if contrasting with the countryside
• in town if talking more locally

Danish often uses byen in a natural, everyday way where English might choose either expression.

Yes. This is standard Danish main-clause word order:

• subject: Mine søskende
• verb: sparer
• other elements after that: op til deres egen lejlighed i byen

So it follows the normal pattern of a simple statement.

One thing to notice is that op comes after the finite verb sparer:

• De sparer op.

This is normal for this kind of verb phrase in Danish.

Yes. Sparer is the present tense of at spare.

Forms:

• at spare = to save
• sparer = save / am saving / are saving
• sparede = saved / was saving
• har sparet op = have saved up

So Mine søskende sparer op... means My siblings are saving up... or My siblings save up..., but in this context English normally uses are saving up.

You can tell from the form of egen in the sentence.

Danish common-gender singular nouns take:

• en as the indefinite article
• adjectives like egen

So:

• en lejlighed
• deres egen lejlighed

If it were neuter, you would expect:

• et ...
• eget ...

For example:

• et hus
• deres eget hus

Yes, that is the most natural reading.

Because the sentence says:

• mine søskende = my siblings
• deres egen lejlighed = their own apartment

it sounds like they are working toward one apartment that belongs to them collectively.

If you wanted to make the idea of joint saving even clearer, you could say something like:

• Mine søskende sparer sammen op til deres egen lejlighed i byen.

But even without sammen, the original sentence already strongly suggests a shared goal.