Well it really depends whats the "language of your heart". Even for people that grow up with 2 langauges there is always 1 language that touches their hearts the most. You know what I mean? 

You can speak both languages perfectly and think in both languages. But heres a way to test it. Which language are you more emotionally drawn to? 

Ex. Lets say there is somebody you know that speaks English & Dutch like you. If this person does something to really piss you off, what language would you yell at them in? Thats a good way to tell which one is your native language. 

At least I think so...

Hi Alexander! To me, being a native speaker is the same as having learned a language or more than one since you were a child. Don't know what age is exactly, but for example, in my case I came here with nine years. Spanish was a very easy language and I'm sure that I could speak it properly in less than 3 months. I just was learning alone with my mom and some books about verbs and vocabulary pictures pretty similar to Roumanian. Pronunciation didn't result to be a challenge and the advantage was that I had the opportunity to live among Spanish people at school and in my own house.

I think that I learned it as my mother tongue and I didn't compare one with another. So, when I began to study English I didn't feel that natural sensation as with Spanish even if I had nine too. I used to say words in English and then see their meaning in Spanish. And then I saw it would take me a lot of time to learn another language. Well, teachers weren't so good and I didn't find English speakers or go to an academy to improve it.

That's why I consider myself as a native of two languages. I can speak and write fluet both of them and I don't translate words from Roumanian to Spanish as it happens me with English. I must admit that my Roumanian is a mix or change of Spanish words haha.

Hope this helps you.

Have a nice day! :)

I would say "yes", it is possible.

But, I have a question:  Which language do you dream in?

well ,I think both of  them are ok .in fact  ,many place have two or there  languages. I  think  it's  normol .don't  you think so ?

If you have no foreign accent in either language and a complete adult vocabulary in both languages and feel totally at home expressing yourself and writing in both languages without the grammatical mistakes that would be made by a foreigner and understand all the jokes and jargon... yep... you're native in both languaes. 

LUCKY YOU!