There was no single source for biographies of members of the Northern Ireland (Stormont) Parliament - no Northern Ireland equivalent of Dods Parliamentary Companion. However there are several sources which do give biographies.
All Unionist MPs and Senators had brief biographies in J.F. Harbinsons book The Ulster Unionist Party which was published in 1973. The source for these biographies was apparently the Belfast Telegraph after each election. Some errors were detected in these biographies. Senior Unionist MPs and Government Ministers were usually invited to contribute to Whos Who.
Those MPs who were also members of the United Kingdom Parliament were also included in Dods Parliamentary Companion and therefore in M. Stenton and S. Lees, Whos Who of British MPs. Successful and unsuccessful candidates in United Kingdom general elections have had biographies in The Times (Guide to the) House of Commons from 1929 to 1997.
Some information on candidates fighting the first three Stormont elections is in Northern Ireland: The Elections of the Twenties by James Knight and Nicholas Baxter-Moore. Some of those active in politics after 1969 are included in Northern Ireland: A Political Directory by Sydney Elliott and W.D. Flackes.
Dates of service in the Northern Ireland Government have been taken from the authors own list.
There are still several MPs who have defied attempts to identify them. Most are Nationalists or Independents. If anyone has any information which should go in their biographies, please get in touch.