The immature distinction only applies to grape brandy, other fruit brandies have no aging requirement or age statement.
As for the rest, the BAM chapter 4 is pretty clear, copied below.
Brandy made by blending two or more specific types of brandies must be identified as “Brandy” followed by the percentage of
(determined on a proof gallon basis) and name of each specific type of brandy, e.g., “Brandy, 25% Dried Pear Brandy, 75%
Lees Brandy”
Percentages are not required if the brandy is derived from:
--2 specific types of brandies and neither contributes less than 40% of the alcohol on a proof gallon basis
--3 specific types of brandies and each contributes at least 30% of the alcohol on a proof gallon basis
--4 specific types of brandies and each contributes at least 20% of the alcohol on a proof gallon basis
Fruit Brandy derived from two or more fruits must be identified as “Fruit Brandy” followed by the percentage of (determined on a
proof gallon basis) and name of each fruit from which the brandy was made, e.g., “Fruit Brandy, 30% Apple Brandy, 70%
Cherry Brandy”
Percentages are not required if the Fruit Brandy is derived from:
--2 fruits and neither contributes less than 40% of the alcohol on a proof gallon basis
--3 fruits and each contributes at least 30% of the alcohol on a proof gallon basis
--4 fruits and each contributes at least 20% of the alcohol on a proof gallon basis