“Third, unlike the Protestant movement, which has splintered
into hundreds of denominations,
Jehovah’s Witnesses have
maintained a united global brotherhood.” Watchtower 2009
Nov 1 p.19


Surely, Jehovah's Witnesses are aware of enough of their history
to know of the Russellites and Bible Student groups that broke away, particularly following
Russell's death, though these groups would claim Rutherford broke away from the true religion as set up by Russell.
It may be said that the quote was referring to Jehovah's Witnesses
specifically since the official name was chosen in 1931, rather than
the Jehovah's Witnesses that have existed since Adam (Jehovah's Witnesses in the
Divine Purpose p., or possibly when the Governing Body is said
to have been chosen in 1919, but even that is not true. New sects have been constantly forming. In
Romania, one group of
Witnesses spent decades isolated during communism, with access
primarily to Rutherford's works. On gaining freedom, they were
offended at the many doctrinal changes in recent Watchtower
publications, and set up The True Faith Jehovah's Witnesses. Since
the Internet, there have been many small splinter groups starting.
Some Breakaway sects with active websites, as of 12 Feb 2013 include:

The True Faith Jehovah's
Witnesses

Bible Fellowship Union

God's Kingdom Society

Christian Witnesses

The Lord's Witnesses

Phoenix Bible Students

Chicago Bible Students

Baltimore Bible Students