Here are the differences between English and Italian possessive adjectives:

1. Italian possessive adjectives are matched with articles:

Examples: la mia casa, la tua macchina, le sue idee, la nostra vacanza, i vostri bambini.

BUUUUT

2. Singular family members do not need article (actually, it is not a difference, it is exactly like in English):

Examples: mio padre, tua madre, suo fratello, vostra figlia. Only singular ones!

3. loro does not change, how can we recognize if it is singular/plural and/or feminine/masculine? C'mon...adding the proper article, right?

Examples: i loro amici, le loro famiglie, la loro casa.

4. This is the most important point: Italian possessive adjectives always refer to the objects/things, NOT to the subject. So, the possessives change gender and number in according to objects/things. Too technical? Let's see some examples:

• My house = la mia casa (it does not matter if the owner is either a "he" or "she", but the house is a feminine word in Italian, is it clear?).

it can get tricky:

• my friend= il mio amico/la mia amica (we can define the gender if we know the contest)
• his car= la sua auto ( who is the owner? Claire or Jack? Again? We do not know, "auto" is a female object in Italian, but it does not mean we know the owner, it depends on contest).