Нас было двое.

Because Russian commonly uses the pattern нас / вас / их + было / будет + collective numeral to say how many people were in a group.

So Нас было двое is the natural way to say there were two of us.

Using мы would sound much less idiomatic here. For a learner, it is best to memorize this as a set pattern:

• нас двое — there are two of us
• нас было двое — there were two of us
• нас будет двое — there will be two of us

Было is the past-tense form of быть, meaning to be.

So the sentence is literally built like:

• нас — us / of us
• было — was
• двое — two as a group

A natural English rendering is there were two of us.

In the present tense, Russian usually leaves out есть, so you would normally say:

• Нас двое — there are two of us

But in the past, you do need the verb:

• Нас было двое

Because this is an impersonal quantity construction.

Even though the meaning involves two people, Russian often uses neuter singular past tense with expressions of quantity:

• было двое
• было трое
• было много людей

So было does not agree with we in the way English were does. The sentence is structured more like there was a group of two of us.

Двое is a collective numeral. It means two as a group.

Russian often uses collective numerals with:

• personal pronouns
• groups of people
• some plural-only nouns

With personal pronouns like нас, вас, and их, the collective numeral is the normal choice:

• нас двое
• вас трое
• их четверо

So Нас было два would not be standard here. Двое is the correct form.

Yes, it can refer to any two people.

With regular nouns, collective numerals are often restricted. For example, Russian normally says:

• две женщины, not двое женщин

But with personal pronouns, collective numerals are perfectly normal regardless of gender:

• нас было двое can mean two men, two women, or one man and one woman

So in this sentence, двое does not tell you the gender.

Not exactly.

• Нас было двое = there were two of us

  • focus: the number in the group

• Мы были вдвоём = the two of us were together / alone together

  • focus: being together as a pair

Sometimes both can fit the same situation, but the nuance is different.

For example:

• В комнате нас было двое.
  There were two of us in the room.

• Мы сидели вдвоём в комнате.
  The two of us were sitting together in the room.

For practical learning, the safest answer is:

нас is the non-nominative form of мы, and in this pattern it works like English of us.

That is why the sentence feels close to:

• two of us

Also, нас has the same form for both genitive and accusative, so learners do not need to worry too much about choosing between those labels here. The important thing is to remember the construction:

• нас двое
• нас было двое
• нас будет двое

Yes, that is grammatical.

But Нас было двое is usually more natural when it is already clear that you are talking about people.

Compare:

• Нас было двое — more compact, more idiomatic
• Нас было два человека — more explicit, slightly heavier

A learner will hear Нас было двое much more often in everyday speech for this meaning.

Yes. Russian word order is flexible, and changing it changes the emphasis more than the core meaning.

• Нас было двое — neutral, standard
• Было нас двое — more literary or storytelling style
• Двое нас было — strongly marked, poetic or stylistic

So if you are learning the basic pattern, use:

• Нас было двое

That is the safest and most natural default.

The same pattern is used across tenses:

• Нас двое. — There are two of us.
• Нас было двое. — There were two of us.
• Нас будет двое. — There will be two of us.

Notice that in the present tense Russian normally does not say есть here. So Нас двое is the normal form, not Нас есть двое.