leur or leurs? when does either apply? in what context - I am confused with the plural.

Question

Accepted Answer

Hi Dragana, you are actually confusing 2 different types of pronouns.
The lesson you refer to is actually about indirect object pronouns. ( me-te-lui-nous-vous-leur ) "leur" in this case means them or to them and it doesn't need an 's' as it is  already a plural, "lui" can be used for a man or a woman and means him /her or to him/ to her. 
There is another type of pronouns called Possessive Pronouns which will be covered by another lesson and there is a "leur" ( singular) and a "leurs" ( plural ) to translate "their ".
e.g. C'est leur frère , c'est leur mère , ( It is their brother, their mother) , Ce sont leurs frères ( These are their brothers) , Ce sont leurs affaires, ( These are their things ). 
The "leur", "leurs" here agree ( singular or plural ) with the noun they refer to.
Hope this helps!

Answer

"Leurs" is used when the noun it refers to is in the plural. An example:

Ils aiment leurs enfants. -- They love their children. 
Ils aiment leur enfant. -- They love their child.

-- Chris.

Answer

This is right, but I think you missed a point. In this lesson we discuss pronouns, that is when you replace people with lui/leur. For example:

Il téléphone à ses parents -> Il leur téléphone

You never replace people with 'leurs', as leurs is not a pronoun.

But there are also what's called "possesive determinants", that you use when someone owns something. English examples might be 'my', 'your', etc. The examples you point out above are possessive determinants, and they can indeed be 'leurs' if their are multiple things that are being owned (sorry for referring to children as things that can be owned, but you get my point).

So if you want to replace multiple people with a word - go with 'leur'.
If you want multiple people to own multiple things - go with 'leurs'.