Welcome to the wonderfully complex world of social security legislation…
http://www.dwp.gov.uk/publications/specialist-guides/decision-makers-guide/#vol5
Also found this on the web but note the years used will be different for your brother and the amounts mentioned increase slightly each year. I also think there was a further change made to the first condition last year.
“You will need to have been employed within the last 2 relevant tax years and have paid, or been credited with, National Insurance (NI) contributions on those earnings”
There are 2 “contribution conditions” which are detailed below:
To satisfy the First contribution Condition, the customer must have:
• paid Class 1 contributions on earnings of at least £2100 in either of the last two Relevant Income Tax Years 07/08 08/09
To satisfy the Second Contribution Condition, the customer must have:
• a combination of paid Class 1 contributions on earnings and / or awarded credits of at least £4200 in both 07/08 and 08/09
• by credits we mean credits that are awarded whilst claiming Jobseekers Allowance, Sickness (ESA) or periods of Approved Training.”