The Jedi Order was founded in 25,783 BBY, and their philosophies --
such as the distinction between the light side and dark side of the
Force -- developed over the next few centuries. They served as the
guardians of the Republic since its foundation. It wasn't until around
4,000 BBY, however, that the Jedi began to forbid marriage and
attachment.
Practically speaking, this is due to the structure of the Expanded
Universe. Before the Prequels came out, EU writers had to avoid the
Prequel Era so as to avoid contradictions with later material. For the
most part, the EU covered events in between the Original Trilogy
movies and after Return of the Jedi. In order to explore new time
periods and characters, works like Knights of the Old Republic were
set 4,000 to 5,000 years before A New Hope and featured Jedi marrying
with no problem. When the prohibition of marriage was revealed in
Episode II, it only made sense in the EU if it started after 4,000
BBY.
In-universe, the new rule prohibiting marriage is justified by changes
in the structure of the Jedi Council and Jedi Order. Before 4,000 BBY,
the Jedi Order was made up of loosely affiliated local groups. After
the Great Sith War, they became a unified organization under the Jedi
High Council, which began to reinterpret the Jedi Code. Among the new
regulations were the prohibition of marriage and the idea that Jedi
must begin their training as very young children.
Source: http://scifi.about.com/od/starwarsglossaryandfaq/a/Star-Wars-FAQ_Why-Cant-Jedi-Marry.htm
Another difference in the portrayal of the Jedi pre- and post-1999 is
the existence of Jedi families. During the Bantam era, it was
established that Jedi could marry and have families, and several of
the characters were the descendants of Jedi Knights, including Kam
Solusar (Dark Empire II; Veitch, 1994) and Corran Horn (I, Jedi;
Stackpole, 1998). Callista had a spouse named Geith Eris, and the
Imperial warship Eye of Palpatine was meant to attack Belsavis, a
planet housing the children of Jedi Knights (Children of the Jedi;
Hambly, 1995). Jedi of the Old Republic during the Sith Era also had
families; Andur and Nomi Sunrider were married and had a daughter,
Vima (Tales of the Jedi: The Saga of Nomi Sunrider; Veitch, 1993).
Then, Episode II firmly established the idea that Jedi could not marry
nor have children, due to the risks of falling to the Dark Side
associated with attachment to your spouse/offspring. Also, according
to Vergere, Jedi were not permitted to have children to avoid creating
Jedi family dynasties, which would have undue influence in the Order
(I think this was from Destiny’s Way; Williams, 2002). As a result,
retcons were required. Ranik Solusar had his son Kam without the
permission of the Jedi Council, and so was severely reprimanded (The
New Essential Guide to Characters; Wallace, 2002). There were two
interpretations of Corran Horn’s circumstance. Either Nejaa Halcyon
had special dispensation to have his son Valin (who became Hal Horn,
Corran’s father) due to cultural considerations (Elusion Illusion;
Stackpole, 2003) or Halcyon married and had a child without
permission, keeping it hidden from the Jedi Council (Jedi Trial;
Sherman and Cragg, 2004). Ultimately, any Jedi offspring dating from
that era (such as Galen Marek) could be explained by the child being
conceived with special dispensation from, or against the will of, the
Jedi Council. Callista and Geith were members of Djinn Altis’s Jedi
sect, which allowed marriage (Order 66; Traviss, 2008). The children
of the Jedi located on Belvasis were retconned into being Apprentices
and Padawans, not offspring (The New Essential Guide to Characters;
Wallace, 2002). Last, issue 23 of Knights of the Old Republic
established that there was a shift in Jedi thinking following the
Great Sith War (J. Miller, 2007). Jedi would continue to have
relationships and families for some years; Grand Master Satele Shan
had a son, Theron (The Old Republic 7; Freed, 2011), but by the time
of the Ruusan Reformations, the Jedi Order would ban marriage and
conception.
source: http://www.eucantina.net/archives/11067
