Q. When the father is divorced and does not attend the Bar Mitzva of his son, should he say the bracha of baruch sheptarani in his shul on that day, not in the presence of his son?
A. Yad Yitzchak (3: 303) and Ginzei Yosef (64) maintain that he should not recite, since the brocho implies that he is standing by his son (Onsho Shelazeh).
Sheilas Shlomo (2: 75) debates whether being in the presence of the son is essential or not and recommends that if the father is not there, he should mention Meonsho Shel B'ni, in third person.
Horav Shlomo Miller's Shlit"a opinion is that since we recite this brocho omitting Hashem's name, he can say the brocho when not in the presence of his son.
Rabbi A. Bartfeld as advised by Horav Shlomo Miller Shlit"a