There are different types of USB connectors. A typical USB cable has two types of connectors, one on each end.
USB Type-A connectors have a flattened rectangular shape. This is the end of the cable that plugs into a USB port on a computer. The end of a USB flash drive ("thumb drive") has a USB Type-A connector as well.
USB Type-B connectors have more of a squarish shape, except that two of the four corners are beveled. This is the end of the cable that plugs into a peripheral USB device, such as a USB printer.
Each type of connector has a male and a female version. I'm referring to the female connector as a "port," and I've been referring to the male connector above as just a "connector."
Whatever you call it, if you have keyboards or synths that have USB ports, either in addition to or instead of MIDI DIN ports, you might notice that some keyboards have both a USB Type-A port and a USB Type-B port. The Type-A port is for plugging a USB flash drive into the keyboard. The Type-B port is for using a USB cable to connect the keyboard to a computer-- the squarish Type-B end of the cable goes to the keyboard, and the flattened Type-A end of the cable goes to the computer.
If you want to connect a keyboard to an iPad, you still have to do the same thing-- plug the squarish Type-B end of the cable into the keyboard, and plug the flattened Type-A end of the cable into the iPad-- except, wait a minute, Apple (in their infinite wisdom, or maybe it's just supreme arrogance) have chosen not to equip the iPad with an industry standard port, and have instead equipped it with a proprietary type of port so that you must purchase special adapter cables, and every so often they change to a different type of proprietary port so that you have to purchase a whole new set of special adapter cables.
So let's look at that cable you've got. One end is a Lightning connector, which goes into the Lightning port of your iPad 5. The other end is a USB Type-A connector, which goes into a computer-- or it can also go into a USB power adapter for charging the iPad; but it can't go into a keyboard unless you plug it into the Type-A port (that is, if the keyboard has one of those), and that port is for loading files from or saving files to a flash drive, not for streaming MIDI data between the keyboard and a computer.
That's why you need to use a Camera Connection Kit to connect a keyboard to an iPad; the Camera Connection Kit provides the iPad with a Type-A port (that is, a female Type-A connector) so you can plug a USB flash drive or the Type-A end of a USB cable into the iPad.
Now, your other cable is a standard MIDI-to-USB cable for connecting a keyboard that has MIDI DIN ports to one of the USB Type-A ports on a computer.
The only way you'll be able to use those two cables to do what you're wanting to accomplish is if you can find a MIDI merger device that has two USB Type-A ports in lieu of two MIDI IN ports, plus a MIDI OUT port so you can send the merged MIDI data to the Ketron SD2.
I won't say that no such MIDI merger device exists, because you could use a laptop as one if you're running an app that can merge MIDI data, although then you'd need another MIDI-to-USB cable for connecting the laptop to the Ketron, or else use the one you've already got for that and use a standard USB cable for connecting the Roland to the laptop. The Lightning-to-USB cable would of course connect the iPad to the laptop.
But other than something like a laptop or desktop computer, I don't know of any low-tech MIDI merger hardware devices that use USB Type-A ports instead of MIDI IN ports.
Some iConnectivity interfaces have a USB Type-A port for connecting a USB-MIDI device, but not all of them do. And those that do have only one USB Type-A port, so if you want to plug both of your cables into it then you'll need to plug your cables into a USB hub and plug the USB hub into the iConnectivity interface. The mio2 that I mentioned won't work, because it doesn't have a USB Type-A port, just two USB Type-B ports for connecting the mio2 to as many as two computers at once. If you want to go the iConnectivity route, I believe you'll need a mio4, iConnectMIDI4+, or mio10, with the mio4 being the least expensive option and the mio10 the most expensive.