XML's Development start around 1996.
The motivation was in part due to the success of HTML and in part due to the crushing need to simplify SGML.
Jon Bosak from Sun Microsystems was the prime motivator for the creation of XML and inspired by Yuri Rubinsky's[1] "SGML on the Web"
The W3C (World Wide Web Consortium) was chosen to host the standards process and the original XML Committee was formed.
The first draft was produced in November 1996 and shown at the SGML conference in Boston, MA in December 1996.[2]
In February 1998, XML became a W3C Recommendation[3].
There is now a "third edition"[4] and XML 1.1 recommendation as of April 2004[5].
[1] http://www.oasis-open.org/cover/yuriMemColl.html
[2] http://www.w3.org/TR/WD-xml-961114.html
[3] http://www.w3.org/TR/1998/REC-xml-19980210
[4] http://www.w3.org/TR/2004/REC-xml-20040204/
[5] http://www.w3.org/TR/xml11/