Los Vs Les
 

Quiero llevarlos al cine esta esta noche (mis padres).

Is it incorrect to use ‘les’ because ‘my parents’ represent the direct object?

Would it make a difference it I were referring to ‘my brothers’ i.e. both male?

Muchas gracias de antemano.

You should use 'los' because it's the correct direct object pronoun in both of the cases you mentioned.

There are some places in Spain where 'les' would be said instead in both cases.
This practice is known as 'leísmo'.

Rusty tiene toda la razón. Y un consejo: ante el leísmo, recuerde aquella frase célebre de Gandalf. En España la tradujeron como: ¡Corred! ¡Corred, insensatos!

Un saludo.