Min søn glemmer altid svømmevingerne, men min datter husker dem.

Because søn and datter are both common gender singular nouns in Danish.

The possessive my changes like this:

• min
  • common gender singular noun
• mit
  • neuter singular noun
• mine
  • plural noun

So:

• min søn = my son
• min datter = my daughter
• compare with mit barn = my child
• and mine børn = my children

Because -ne is the ending for the definite plural in this word.

The noun is:

• singular indefinite: en svømmevinge
• plural indefinite: svømmevinger
• plural definite: svømmevingerne

So svømmevingerne means the swim wings / the water wings.

In this sentence, the speaker is talking about a specific pair/set that the son is supposed to bring, so Danish naturally uses the definite form.

Danish, like English, often forms compound nouns, but Danish does this very frequently and writes them as one word.

So:

• svømme = to swim
• vinge = wing
• svømmevinge = swim wing / water wing

Then the plural definite form becomes svømmevingerne.

This is very normal in Danish. English sometimes keeps similar ideas as two words, but Danish usually prefers a single compound noun.

Because dem is the object form of they.

• de = they, the subject form
• dem = them, the object form

In this sentence:

• min datter husker dem
• my daughter remembers them

Here, them is the thing being remembered, so Danish uses dem.

Compare:

• De ligger i tasken. = They are in the bag.
• Jeg tager dem med. = I’m bringing them.

This is normal Danish word order in a main clause.

The basic pattern is often:

• subject + verb + adverbial

So:

• Min søn glemmer altid svømmevingerne.

That is why altid comes after the finite verb glemmer.

This is different from English, where adverbs like always often come before the main verb:

• English: My son always forgets...
• Danish: Min søn glemmer altid...

Because Danish verbs do not change for person or number in the present tense.

So:

• jeg glemmer = I forget
• du glemmer = you forget
• han/hun glemmer = he/she forgets
• vi glemmer = we forget

The same happens with husker:

• jeg husker
• du husker
• hun husker

Unlike English, Danish does not add a special -s for he/she/it.

Because men means but, and in standard Danish punctuation it is very common to place a comma before it when it joins two main clauses.

Here the two clauses are:

• Min søn glemmer altid svømmevingerne
• men min datter husker dem

So the comma helps mark the contrast clearly.

In this sentence, repeating min is the natural and clear choice:

• Min søn ... men min datter ...

It creates a neat contrast between the two children.

If you removed the second min, the sentence would sound less balanced and less natural in this context. Danish often repeats possessives when comparing or contrasting two different people or things.

So repeating min is not just acceptable; it is the best phrasing here.

It can be singular:

• en svømmevinge = a swim wing / water wing

But in real life, people usually use them as a pair, so the plural is very common:

• svømmevinger
• svømmevingerne

That is why the plural feels especially natural in this sentence.

Yes. glemmer is the present tense form of glemme.

For the two verbs here:

• at glemme = to forget

• glemmer = forget / forgets

• at huske = to remember
• husker = remember / remembers

A very common pattern in Danish is:

• infinitive often ends in -e
• present tense often ends in -r

Yes, that would be grammatically possible:

• Min søn glemmer altid svømmevingerne, men min datter husker svømmevingerne.

But it sounds repetitive. Danish, like English, usually prefers a pronoun when the noun has just been mentioned.

So dem is the more natural choice.

Yes: after men, the next part is still a main clause, so normal main-clause word order stays in place.

That is why you get:

• men min datter husker dem

not a subordinate-clause pattern.

The order is:

• men
  • subject
    • verb
      • object

This is useful because some Danish conjunctions keep main clause word order, while others introduce subordinate clauses with different word order.

You could still keep the same sentence, because altid already gives that meaning clearly:

• Min søn glemmer altid svømmevingerne...

If you wanted stronger emphasis in speech, you would usually do it with intonation, not by changing the grammar.

You might also move another element to the front in a different sentence, but the version you have here is the most straightforward and natural standard wording.