The word used in Acts 2:3 is διαμεριζομεναι which is exactly the same as that used in Mark 15:24 and in Luke 23:34 for the activity of the soldiers parting or dividing the garments of Jesus among themselves.
It seems highly unlikely that there were only two soldiers involved in the execution by crucifixion of three persons. Thus, in that case, 'parted' or 'divided' would, almost certainly, indicate more than two parts being separated.
So I would suggest that the word itself, alone, does not convey how many parts the tongues were parted or cloven into.
The word appears to only convey that a parting occurred.
The literal wording of :
διαμεριζομεναι γλωσσαι ωσει πυρος εκαθισεν τε εφ ενα εκαστον αυτων
[Received Text - Stephens, Beza, Elzevir and Scrivener are all identical]
is as follows :
divided tongues as of fire and sat upon one each of them [EGNT]
divided tongues as it were of fire it sat also upon each one of them [Young]
(The KJV conveys 'cloven tongues' and 'it' sat upon each of them.)
The three translations above seem to me to indicate that something mysterious is being conveyed and there is doubt among the translators as to what is happening.
My own thought is that there is one source of fire, divided. And it is the divisions of fire that are being described as 'tongues'. And the same fire sits upon each of them, since a tongue of fire reaches each individual.
Thus what appears, in a supernatural manifestation, conveys two things - the unity of being invigorated by a single source and the individuality of each one being granted a fiery tongue with which to express themselves.
But I would not wish to argue that interpretation in the context of a mysterious
occurrence which valid sources have found difficult to translate. I only offer the suggestion.