He attended Western Illinois University where he earned a bachelor's degree in business administration.

[1] He then became co-owner and vice-president of Sieben Hybrids, a family seed business and he operated a 400-acre livestock farm.

During his time in the House he praised lifting the inheritance tax, attempted to shorten campaigning season by moving back Illinois's March primary elections and was supportive of education reform with the exception of forced school district consolidation.

[4][5] After the 2001 redistricting, Sieben's district was renumbered to the 45th, and drawn to include all of Jo Daviess, Stephenson and Lee counties and portions of Winnebago, Ogle, Carroll, Whiteside and Henry counties.

In 2007, he announced his retirement, but in February 2008 he chose to resign to become a lobbyist for the ethanol industry.