Sometimes the question arises regarding how a person should practice when his father, who is a member of one ethnic group, becomes accustomed to praying in a nusach of a different ethnic group. Should he pray in the nusach in which his father currently prays or in the nusach of his father’s ethnic group? As a general rule, the obligatory minhag is that of the ethnic group and not one’s father’s individual minhag. However, when the son prefers to continue in his father’s adopted nusach, or because he finds it difficult to change, or for any other reason, he is permitted to continue praying in his father’s nusach. Since this question poses implications on other issues, it is best that one consult with his rabbi on this matter.
A similar dilemma arose among members of Chassidic families, who learned in Lithuanian yeshivot and became accustomed to praying in Nusach Ashkenaz. When they left the yeshiva, they deliberated whether to continue praying in Nusach Ashkenaz as they were taught in yeshiva, or return to praying in Nusach Sephard–Chassidi, the minhag of their parents.
The rabbis of the Ashkenazic minhag taught that, in principle, they must continue praying in Nusach Ashkenaz, for in the past, all Ashkenazic Jews prayed in Nusach Ashkenaz, and only 200 years ago did the Chassidim change their nusach. Even though now, after such a long time, all Chassidim will not be instructed to return to pray in Nusach Ashkenaz, still, it is best that those Chassidim who already became accustomed to praying in Nusach Ashkenaz continue to pray that way, because it is their ancestors’ original nusach. However, the Chassidic rabbis insisted that they must continue in the Chassidic nusach, reasoning that since prominent Chassidic authorities have instructed those who prayed in Nusach Ashkenaz to switch to the Nusach Sephard–Chassidi, in congruence with the writings of the Ari, all the more so, anyone born into a Chassidic family must continue praying in the Chassidic nusach.
In practice, since there are differing opinions, the person posing the question may choose how to practice. Still, it is best to consult with one’s rabbi on this matter.