Ambilingual

The ambilingual poet (as I regard myself) dealing in the transcription of his or her own poetry, though one would assume able to take more liberties, ends up having more trouble in fashioning equivalents.

Source: wiktionary

Some bilingual speakers, including some who are ambilingual, can be said to have two (occasionally more) native languages. There is no exact criterion for this; but one could say arbitrarily that any language learnt by the child before the age of instruction, from parents, from others, such as a nurse, looking after it, or from other children, is an L1. It is clear, however, that only a small proportion of those who learn two or more languages in this way become ambilingual speakers; and conversely, not all ambilinguals have two L1s.

Source: wiktionary

But true ambilingual speakers are rare as most of the bilingual speakers restrict at least one of their languages to certain uses.

Source: wiktionary

When two languages in a territory function for the same people and both can be used officially and at the dialect level we have what is called an ambilingual situation.

Source: wiktionary