Spanish language Q&A Forum

Hola to whoever sees this:

RE: Exercise: Theatrical courtyards at: 

https://spanish.kwiziq.com/my-languages/spanish/exercises/judge/230/459630?response=61964&page=12

Last translation in the exercise: 

and their history is interesting.

Kwizbot y su historia es interesante. 

You y su historia está interesante.

I was wondering why ser is used here instead of estar.

Thank you. Nicole

Puse solo la mitad de la harina en el bol.

I only put half the (quantity of) flour in the bowl.

Ella tiene el doble de hermanos que él.

She has twice as many siblings as he does.

Why is it de LA harina, but not de LOS hermanos? Is the definite article always skipped after doble de? There was a quiz question for "________ tiempo" meant to be filled with doble. Would it be "el doble de" or "el doble del"? 

I was marked wrong for answering "Nosotros LES damos juguetes a nuestros hijos" instead of just "damos" I thought that the indirect object pronoun HAD to be used. What am I missing? When should I be using it? 

Thanks.