The Stepfather in a Kesuba
‘He Was the Stepson of Kenaz’
The Gemara asks why the Torah calls Kalev the son of Yefuna (Bamidbar 13:6) when in Sefer Yehoshua (15:17) we learn that the name of the father of Asniel – Kalev’s brother – was Kenaz. If Kalev and Asniel were brothers, how could Kalev’s father have been Yefuna and Asniel’s father Kenaz? The Gemara explains that they were half-brothers; they had the same mother but different fathers. Kalev was called “Kenizi,” however, in deference to his stepfather, Kenaz, who raised him.
The Kesubah of an Adopted Child
Based on this Gemara, the Minchas Yitzchak (4:151) answers an interesting question concerning an adopted girl who has never been told she was adopted. When a woman gets married, her father’s name must be recorded in her kesubah, but what if her adopted parents fear that the news that she is not their biological child will upset her terribly?
The Minchas Yitzchak ruled that if an adopted child is emotionally stable, it is best to write the name of her real father in the kesubah. Otherwise, her real lineage might be forgotten, and either she or her children might end up marrying biological relatives from her real parents.
However, if the adopted daughter is unstable and it might damage her mental health to learn the truth, the Minchas Yitzchak writes that we should change the language of the kesubah slightly so as to hint to the truth. For example, if her name is Sarah, and her adopted father’s name is Avraham, we should write, “Sara, who is called Sara daughter of Avraham,” rather than, “Sara daughter of Avraham.”
The Minchas Yitzchak explains that Kalev was called “Kenizi” rather than “son of Kenaz” – even though our Sages tell us that a person who raises an orphan in his home is considered that child’s biological father (Megilla 13a) – so as to provide a lasting hint that Kenaz was not his real father and thus prevent forbidden marriages among relatives.
Aliyah to the Torah for those Adopted
The Minchas Yitzchak addresses a similar question concerning calling up a bar mitzvah boy to the Torah who does not know he’s adopted. In this case, the Minchas Yitzchak rules that we must use his father’s real name to prevent the chance of a forbidden marriage. Rabbi Yosef Sholom Elyashiv rules similarly (Ha’aros Maseches Sotah, p. 68).
(All this obviously only applies to a child who was born Jewish. A child born to non-Jewish parents must be informed of his childhood geirus before he reaches age 13 and given the choice of either accepting his geirus or rejecting it.)