Russian Collective Numbers

Did you know that, apart from ordinal and cardinal numbers, there are also collective numbers in the Russian language, such as: двое, твое, четверо, пятеро, шестеро, семеро.

They are only used in some particular cases:
1. when we speak about two or more men or a group formed by men and women.

Двое сотрудников пошли на обед.

2. when we speak about animal cubs.

Кошка родила твоих котят.

3. when we speak about objects that only come in pairs.

Я купила в магазине двое брюк.

Collective numbers are used with  nouns in Genitive plural (when the whole expression is used in the Nominative case or Accusative inanimate) and have their own declination.

N. двое коллег
G. двоих коллег
D. двоим коллегам
A. двоих коллег
I. двоими коллегами
P. двоих коллегах