American Express is offering a 1000 JP Miles for the holders of the Jet Airways American Express Platinum Credit Card, when they choose to enrol an add-on card holder from their family for the card. The promotion is valid between May 1, 2015 to May 31, 2015.
You can apply for up to two free add-on cards from your family members above 18 years of age (parents, kids, siblings and spouse), and for each completed application you can receive 1000 bonus JP Miles. The miles would be deposited in your JP account by July 2015. The supplementary cards may or may not be issued, but the miles are guaranteed as long as you get the application across by 31st of May 3015.
Here is the form for requesting supplementary cards [PDF].