"He is my brother."
Translation:È mio fratello.
The rule is that for singular close relatives you dispose of the "il" bit. (The "possessive pronoun" - also "la" for the feminine) So it is mia moglia, mio fratello, mia sorella etc.
The problem there is that I said "il mio padre" earlier and it counted it as correct.
They obvi didn't want to make a big deal out of it...but "mio padre" is correct.
We should remind that "il/la (as the in English) comes from the L. demonstrative" ille/illa" =that. Now we can have different things we have only a father and mother
There are a few things wrong with "lui i miei fratello".
First, there is no verb. You would need to say "lui è i miei fratello."
Second, you have the possessive in the plural, but the noun is singular. You would need to say "lui è il mio fratello" in the singular or "loro sono i miei fratelli" in the plural.
Third, singular family members don't take the definite article as part of the possessive phrase. So the correct way to say "He is my brother" is "Lui è mio fratello."