user: Question: What is Assembled, when 2nd Member is "unknown"?
Columns: ['Summoned', 'Elected', 'Assembled', '1st member', '2nd member']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['30 September 1295+', '1295', '27 November 1295', 'John Cullebere', 'Simon de Holand']
SQL:

assistant: SELECT "Assembled" FROM "Table" WHERE "2nd member" = 'unknown';