One page should own the whole keyword family when the variants all share one intent and surface one set of search results, and you split it when a variant carries a distinct intent or its own results page that deserves separate treatment. The pivot is shared intent versus distinct intent: same need, one page, different need, two pages. Neither extreme is right, building a page for every variant fragments your effort, and cramming genuinely different intents onto one page leaves each underserved.
Keep the family together when the variants are just different ways of asking the same thing. “How to clean a cast iron skillet,” “cleaning cast iron pan,” and “cast iron skillet cleaning steps” all want the same answer and would return the same kind of results, so one strong page owns them all. Splitting them only manufactures internal competition, where your own pages dilute each other for queries a single page could have won outright. The shared intent is the signal that they belong on one page.
Split when a variant breaks away into its own need. “Cast iron skillet cleaning” and “how to remove rust from a cast iron skillet” start in the same family but diverge: the rust query has a distinct intent, a different answer, and likely its own results page where dedicated pages rank. That variant has earned its own page because serving it well requires content the general page would not naturally carry. The test is not how similar the words look but whether the searcher behind the variant wants something the family page cannot fully deliver.
So before deciding, look at intent and the results pages, not the keyword spelling. Keep same-intent variants on one page that owns them cleanly, and peel off only the variants whose intent or results genuinely diverge, giving each of those its own page. Group by the need, split by the difference, and let the family hold together everywhere the intent is one.