Have you tried having the Helix first in the midi chain - it can be set to pass on everything via its midi out.
Also - if you're only sending midi to 2x devices - try a midi Y splitter cable to send midi in parallel to the Helix and Kemper . I have a 'midi through' box that takes the midi signal from my helix and sends it in parallel to the 4 midi devices in my rack - so no need to switch everything on just to get midi to the last device in the chain.