Abraham Maimonides

Maimonides' only son, and after him the Nagid — head of the Jews of Egypt. He led a pietist circle (ḥasidim) that adopted Sufi disciplines outright: nightly vigils, extended solitary retreat, weeping, prostration, and prayer in rows facing Jerusalem with hands raised. His great Judeo-Arabic guide for worshippers argues that these practices are not borrowings at all but the lost discipline of Israel's own prophets, preserved by the Sufis while Jews let it lapse — a claim he makes in writing, to his own community, with his father's authority behind him.

The most extraordinary node in the entire annex. Every other cousin converged from far away. This one is a documented, public, argued adoption by the head of a Jewish community — and it provoked exactly the fight you would expect: some of his congregation petitioned the Muslim authorities to stop him introducing "gentile" innovations into the synagogue.