In Spanish we have the word mano for hermano ("brother"), and that form can give the diminutive manito, when the brother is very small (less than one). In Latin, like in Italian, it might be possible to shorten frater to fra.
Now, the question is: how can we make fra diminutive? Of course, there exists fraterculus, but that's the diminutive of frater. This would need to be a diminutive of fra. Perhaps fraolus?
Summary: is it possible to truncate frater, like fra in Italian? If so, can a diminutive of this truncated form be constructed, as in Spanish?