The Surinder Singh Route is available to direct family members of an EEA national. These family members are outlined in Article Two of Directive 2004/38/EC.
Children of either the EEA National or their spouse Who are either under 21 or Over 21 and Dependant on their parents
Dependant Parents/Grand parents of either the EEA National or their spouse
Obviously there is still the possibility that this position could be expanded by the ECJ to include extended family members but this is not currently the case.
UPDATE: In case C-456/12 it appears clear that Extended Family Members will not benefit from Surinder Singh.