All applicants over 18 years old must meet the English language requirement, but the main applicant may be exempt if they have meet the English language requirement in a previous visa application. Information on the different ways ILR applicants can meet this requirement, and the various exemptions from having to meet this requirement, is found in Home Office guidance.
While Skilled Worker (previously called Tier 2), and some other visa holders may not need to meet the English language requirement as they met this in a previous visa application, their dependants who are over 18 years old will normally have to meet this requirement.