Combining units

[Loucipher]

Yes, it is true. Mercenary units cannot merge either.
It was stated somewhere within the Guild that they actually can be merged (namely when both units have exactly the same valour and upgrades, and neither of the generals has V&Vs), but my thorough testing has showed that they never can - not even in the above described case.
If they take losses, the only option is to fire them - or let your enemy do it for you

[Ludens]

Yes, it is true. Mercenary units cannot merge either.
It was stated somewhere within the Guild that they actually can be merged (namely when both units have exactly the same valour and upgrades, and neither of the generals has V&Vs), but my thorough testing has showed that they never can - not even in the above described case.

It used to be possible to merge mercenaries in vanilla M:TW, but either the first patch or VI put an end to this.