I was born in the US and stayed for a little over 2 years, thus English and Spanish (my parents' native languages) are both my native languages. I've stayed in near constant contact with English and never lost the language even if I was raised for the rest of my life in a Spanish speaking country.
I'm currently looking for scholarship options abroad, and most will require me to take an English proficiency test as if learned as a second language (like the TOEFL or IELTS exams), which is not the case. I haven't been able to find any information on how scholarship language requirements work for native speakers and even then, I'm not sure how I could prove that it is, indeed, one of my native languages.
Is there any certificate that I could get to prove that I'm a native speaker? Or would I have to take one of these exams despite that anyway? I'm aware my situation is uncommon so I don't know if any information is available; either way I appreciate any kind of advice or info anybody has on this.