The JWs (formerly known as Bible Students) have suffered a great deal of schism so this question is a case of the pot calling the kettle 'black'.
JWs have been told that around the 1920s the break-away then was a bit of a blip. Really? Two-thirds voted with their feet! Here is but one example of a splinter group prior to the Big One in the 1920s:
The Friends of Man were founded in 1916 by Alexander F.L. Freytag, the former Branch manager of the Watchtower Society’s Swiss branch since 1898. He founded a group first called the Angel of the Lord, Angel of Jehovah Bible and Tract Society, then Church of the Kingdom of God or the Philanthropic Assembly of the Friends of Man. Freytag claimed he was the legitimate successor of their first president, CT Russell. The second President, J Rutherford ousted him from the Watch Tower Society in 1920.
In Italy, Turin, the first community was founded in 1946 by Sebastiano Chiardola. They are against the Trinity doctrine, believe in the one God Jehovah and are vegetarian. In 1951, the name was changed but they were still going strong. Their weekly 4 meetings are largely devoted to study of the founder's writings. Baptism and the Lord’s Supper are celebrated only within the Swiss branch, not in France. Regional meetings are also organized in European countries, Algeria and Morocco. An elder looks after a congregation. The 71,500 members are active in 20 countries.
When Freytag died in 1947, one of his followers, Bernard Sayerce (1912–1963) claimed he was his successor. Almost all of the 900 French and Belgian assemblies joined this new group which had a peak of 9,700 members between 1958 and 1962. In 1963, Lydie Sartre (1898–1972), who was named the "Dear Mom", then Joseph Neyrand (1927–1981) in 1971, replaced Sayerce as leaders of the movement, named "Amis sans frontières" in 1984.
There can hardly be a JW alive today who knows anything of that one splinter group. There are other splinter groups, such as the Associated Bible Students, and Dawn Bible Students, who still exist. The minority group that stuck with Rutherford in the turbulent 1920s and 1930 accepted his accusation that those groups were "the evil slave" of Matthew chapter 25. They had no contact with them whatsoever and very few JWs today know anything about them, or more recent splinter groups such as The Lord's Witnesses (circa 2000, in England).
One reason why modern JWs gloat publicly about "remaining united" is that such knowledge has been kept from them. If they knew the true extent of all the splinter groups in their 140 year history, they would burn with embarrassment at this question!