That s true for either dc fans or pwm.
Connect two case fans to one header.
Each fan header is rated for up to 1 amp.
If the total current drawn by the two fans is less than that rating they can share the header but not if the total current exceeds 1 amp.
Second part will be about connecting up to 6 fans using same tools as in first case plus 4 pin molex cable and electric tape or shrinking tube or soldering iron tape.
The easiest and cheapest option is to obtain a y splitter for the 2 fans and control them both with a single fan mate fan mate plugged into mother board then splitter going to the 2 fans.
This then leaves the other single fan and header conection to the motherboard for control.
This guide will divide in two parts.
It usually works to connect two fans to one header with a splitter cable.
If you want absolute control over your fans the best option would be a dedicated fan controller.
Although you could try connecting 2 fans to each header and not using one of the rpm wires they should be the same anyway and yes they will be controlled as if they were one fan.