If someone born not Jewish was raised by a Jewish family and accepts upon themselves Judaism at the age of bar mitzvah, what should he say is his mothers name? The question is further complicated because the woman who raised him (and in all intents and purposes is his mother) would get hurt if he uses a name other than her own. For example: The boys name given to him at his bris is "Eliyahu", and the woman who raised him jewish is called "Nechama" would it be proper for him to be known when needed as Eliyahu Ben Nechama? (same question for the father who rasied him)

ב"ה Although, you seemingly asked a simple question, I think a ruling on an issue like this is to be dealt with by a local Rabbi or Bet Din, because of the ramifications of marriage in the future. However, I will give some general guidelines, A converted child may refer to his or her adoptiing parents as his or her parents and that would be considered a lie, since thay are raising him. This is the opinion of many poskim. As far as using the name of the parent, the only time in an official way the name of the mother of a person is mentioned is when they are prayed for when they are ill. The predominant custom is that a convert is called the "….. the son of Avraham Avinu and some even say that a convert even when being prayed for instead of calling the convert the son of Sara, " the son of Avraham Avinu " should be said. However, Rav Shlomo Zalman Oirbach zt"l is quoted ( נשמת אברהם חושן משפט סי' מ"ב) for having said, that if a convert is called up to the Torah ,if the name of the bioligical father is known it should be used . If not, then the name of the adoptive parent may be used. As known women are not called to the Torah, but the same priciple would apply in regard to the name of a girl and the name of the adoptive mother. May you have a very happy, kosher and HEALTHY Pessach. All the best