If for example we would say:
I consider you as a brother.
I consider you as my older brother.
How can we translate those sentences into German, because I don't know how "etw. für ... halten" is used in such sentences.
You might say:
A German will probably understand what you mean, but there are other words for expressing this, such as:
The phrase etw. für etw. halten might be better used in sentences like the following:
Most of the time etw. für etw. halten also implies a “but it wasn’t true”, e.g., the last example sentence is only used, if es actually was possible.
Actually, "I consider you as a brother" (in the sense of: "Even though we are not related, you are more than just a friend to me" or "I know you are not my brither, but I treat you like my bother") would rather be "Ich betrachte dich als meinen Bruder" or "Ich sehe dich als meinen Bruder an". On the other hand "Ich halte dich für meinen Bruder" would imply that I actually think you are my brother (e.g. because I only hear your voice via phone and you sound like him)