This is the 8612th most frequent Polish word.
przyrodni
"Przyrodni" means "step-" or "half-" when referring to familial relationships (e.g., stepbrother or half-sister).
Here, 'przyrodni' modifies 'brat', meaning 'stepbrother', indicating a relationship not fully by direct family bond.
Mój przyrodni brat zawsze mnie wspiera.
My stepbrother always supports me.
In this example, 'przyrodnią' (feminine form of 'przyrodni') describes 'siostrę', meaning 'stepsister', showing its use for gender agreement with the noun.
Czy wiesz, że Marta ma przyrodnią siostrę?
Did you know that Marta has a stepsister?
The word 'przyrodnim' is the masculine instrumental form of 'przyrodni', applied to 'kuzynem', indicating a relevant family connection.