I am building a custom basemap which includes address labels. Some of the address points (in apartment buildings, for example) are all on the same XY coordinate, or within 2 meters of each other. The client has asked to combine these labels into a single label.
Example 1: 3 addresses on the same XY point (2, 2A, and 2B) they would like this displayed as one label (2, 2A, 2B)

Example 2: 267 addresses on the same/similar XY point; they would like this displayed as a range in a single label (1-267)
What makes Example 2 slightly more complicated is that these types of addresses meet a specific criteria:
[HOUSE_LOW] != [HOUSE_HIGH] and [FLAT_LOW] == [FLAT_HIGH]
label to display: [FLAT_LOW] / [HOUSE_LOW - HOUSE_HIGH] (example: 267/9-17)

I can't use the "remove duplicate" option in the labeling properties because they are not all technically duplicates; they each have a different prefix (FLAT_LOW) on the XY point.
Is there any way to achieve this using the labeling classes and expressions in ArcGIS Pro? I would need to be able to reference other addresses within a certain distance that share the same HOUSE_LOW and HOUSE_HIGH values but differ in FLAT_LOW values, then get the minimum and maximum FLAT_LOW to create the range of FLAT_LOW values.