Ekki rugla mér saman við systur mína; við erum ekki eins.

In Icelandic, ekki + infinitive is a very common way to give a negative command:

Ekki rugla ... = Don’t confuse ...

So even though rugla is the infinitive, the whole expression works as a prohibition or warning. You can also hear forms like Ruglaðu ekki ..., but Ekki rugla ... is extremely natural and common.

This is a fixed expression:

rugla einhverjum saman við einhvern = to confuse someone with someone

Its parts are:

• rugla = confuse, mix up
• einhverjum = someone, in the dative
• saman = together / mixed up
• við einhvern = with someone, after the preposition við

So the whole structure is not just word-for-word; it is an idiomatic pattern you learn as one unit.

Because this expression takes the person being confused in the dative case.

The pronoun forms are:

• ég = I
• mig = me (accusative)
• mér = me (dative)

Since rugla einhverjum saman við einhvern uses dative for the first person, the sentence needs mér.

Because við here takes the accusative case, and both the noun and the possessive have to match that case.

The base form is:

• systir mín = my sister

But after við, it becomes accusative:

• við systur mína = with my sister

So:

• systir → systur
• mín → mína

Because they are two different words that just happen to look the same:

• við in við systur mína = the preposition with
• við in við erum = the pronoun we

This is very common in Icelandic. Context and grammar tell you which one it is.

That is the normal Icelandic pattern. Possessive pronouns very often come after the noun:

• systir mín = my sister
• systur mína = my sister (accusative)

So for an English speaker, the word order may feel reversed, but in Icelandic it is completely standard. Putting the possessive before the noun is possible in some contexts, but it is usually more marked or emphatic.

Because erum is the 1st person plural present tense of vera (to be), and the subject is við (we).

A few present-tense forms of vera are:

• ég er = I am
• þú ert = you are
• hann/hún/það er = he/she/it is
• við erum = we are
• þið eruð = you are
• þeir/þær/þau eru = they are

So við erum simply means we are.

Here eins means the same or alike.

So:

við erum ekki eins = we are not the same / we are not alike

This is a very common use of eins with vera. It does not change for gender or number here.

Yes. A common alternative would be við erum ólíkar if two women are speaking, or við erum ólík in a more general citation form.

But við erum ekki eins is simple, natural, and very idiomatic. It emphasizes that the two people are not alike.

It can work for either, depending on context.

One useful thing about ekki + infinitive is that it does not explicitly show singular or plural. So:

• it can be said to one person
• it can be said to several people
• it can even sound like a general warning or instruction

That is one reason this pattern is so common in Icelandic.

The semicolon links two closely related full clauses:

• Ekki rugla mér saman við systur mína
• við erum ekki eins

It shows that the second clause explains or supports the first one. A full stop would also be possible, but the semicolon makes the connection feel tighter.