Candidate for a reserved presidential election

What should be the criteria for a candidate to qualify under a reserved presidential election?

Should both parents come from the reserved ethnic group? Is it acceptable if one one parent come from the reserved group, i.e. a mixed marriage? Should the spouse also come from the reserved group?

You can see the results of the voting by the Crowd here:
http://www.wisdomofthecrowd.sg/chart.aspx?ID=59