Today is the yahtzeit of Rabbi Shmuel Schneersohn, the 4th rebbe of Lubavitch. Chabad.org incorrectly notes:
After the death of the saintly Tzemach Tzedek in the spring of 5626 (1866), Rabbi Shmuel was elected to succeed him as head of the Chabad Chassidim.
In actuality, there were four other brothers, older (and some say wiser) than Shmuel, who sought the post of Rebbe of the town Lubavitch. These brothers already were rebbes of other towns, having been sent to them years before by the Tzemach Tzedek. Shmuel was not. Shmuel fought them and eventually retained control over the town of Lubavitch and the graves* of the Mittler Rebbe and the Tzemach Tzedek. But he was not the rebbe of all or even most of Chabad hasidim. Most followed the other brothers. In fact, streams of Chabad hasidut other than Lubavitch existed into the 1950's. Agudas Chasidei Chabad, a.k.a. Aguch, was founded by an amalgum of different Chabad streams, most prominently Bobroisker.
*The graves were a major source of income for Shmuel and were an important reason he retained prominence.