A control room is full of lamps. Each lamp has a constituency: the encoder engineer, the duty editor, the steward, the lighting gallery. When those people share one wall sheet, they each look for their own number and miss the one that moved.
We use “metric family” for numbers that share a clock and a decision. Stream health with audience share is a family because a bitrate drop and a viewer dip can be argued in the same minute. Occupancy with throughput is a family at a door. Load with lag is a family on an outgoing path. Encoder temperature with merchandise take is not a family. It is two rooms taped together.
Clients sometimes ask us to add “just one more line” after the ink is dry. We decline. A second family is a second board, or a second briefing. The wall can hold two sheets. It cannot hold a sheet that tries to be the whole truck.