Hi there, I’m maybe a little bit late but I program robots and PLC, so I think I can help you. Kuka with ProfiNET M/S can be a “master” and have profinet “slaves” but S7 Siemens plc GSDML isn’t easy to find… so this isn’t the best option to go with. If you just need to communicate with another PLC that is a S7 PLC, you just need to add the other plc to your TIA-Portal project (within the same profinet network and correct IP settings) and use the PUT/GET system function. This is the best way to communicate with two S7 PLC because if one PLC is shutdown, the other will not stop because missing module like it would if is set has an I-Device or an IO-Device.
If you need to communicate with the robot, just send data from your PLC, to the master PLC (with PUT/GET commands) and make sure the master PLC will send that data to the robot and vice-versa.
If you have more question you can ask. Ty