Bluetooth device only try to pair Samsung Galaxy S3 but not HTC Sensation or Samsung Galaxy Nexus Bluetooth device supports Bluetooth 2.1 so no keying PIN necessary.

All 3 Android phones Samsung Galaxy S3 with Android 4.1.2, HTC Sensation with Android 4.0.3 and Samsung Galaxy Nexus with Android 4.1.2 are running the same app - BluetoothChat app by Google targeting Android API level 15 (4.0.3). 3 apps on 3 phones were listening to incoming connections (Serial Port Profile I suppose) but only Samsung Galaxy S3 gets asked to allow or disallow pairing. I've tried doing the same test with each individual device and each pair of them but the result is the same.

Any ideas why this is happening?
By testing with Another device (Xperia Z running Android 4.2.2) I've discovered that the Bluetooth pairing prompt is actually a Jelly Bean's feature which is not available in Ice Cream Sandwich or earlier version of Android