A suggestion.
This site is from a Swedish dealer but the same product would Y find at any corner of the world.Or Y could make it by twisting the wires together.
Fläkttillbehör - Inet.se
It's just a divider "Y" wires one with 3 and the other with 2 "parts".
Two are for power and the third is for "rpm signal"
As Y friend said use the same wire for signal.
(borrow this one by connecting in parralell="cross-connected the RPM signal" )
In other words by connecting more then One fan they will adjust (fed with volt up to 12V)
according to the fan that give 'rpm Signal".
You can connect fans up to the limit of the channel.The fan controller see:
Kaze Server 5.25 : Scythe EU GmbH
Accordin to the spec:
Number of Fan Control Channels:
4 (Max. 1 Ampere and max. 12 W per Channel)
I hope Y understand (no pictures) and Y have any fans with 3-pins to give a rpm signal