Combining fleets togehter impossible?

Hey, what's about combining fleets?
I'm playing my Roman campaign, it's about 257 B.C. and I begin to need some fleets to protect my Sicilia, Sardinia and Corsica from Carthaginian naval assaults. However, after I produced some ships (now I have 4 Pentekonterai and 2 Triremes), I wanted to make one or two stronger squadrons, with 1 Trireme and 2 Pentekonterai each. Yet it was impossible!
I can't add any fleet to another, and it seems that I'll have to sail with single ships! What the heck?
Is that a way to improve AI fleets? As I remember, the AI when moving troops by sea uses only 1 ship and rarely construckts any fleet stacks; is that the reason?
Or maybe there's a bug somewhere?

If one of the admirals has a better quality ship he'll refuse to give up command to the other.
If one of the admirals has is a better general he'll refuse to give up command to the other.

So if your pentekonteroi one is the best, the only solution on this level is to let him depart for one of your docks and let him sit in the dock whilst a trireme is trained at the same location. Then he'll be using a trireme for flagship which allows him to merge with other, lesser trireme-admirals.

All the other ships can be simply separated from the pentekonteroi flagship and merged with the other fleets.

EDIT: Not to mention what beatoangelico mentioned....

it's a known issue, it will be fixed with 1.1 I think. The problem IIRC is that Roman admirals have an hidden trait that adds the cognomen, and is not possible to merge 2 fleets if the admirals have any trait.

...although you can just move the non-admiral ships to the other fleet without much difficulty in most cases; "captain" admirals without any traits and such don't seem to count, although dunno about the Romans.

Well, all my Roman admirals are "captain" (or whatever?) - they have full Roman three-part names with cognomen etc., none of them has any trait; one Pentekontera has 2 bars, others have not.
Does weapon quality counts to be "better ship"?
And even when having Trireme, I couldn't add any Pentekontera to Trireme...

Cognomens are not really names (because those are assigned randomly) but *hidden* traits. Internal workings to represent the crazy Romani. :shrug: