Currently, the "Next of Kin" questions are located in the Extended ILR section of the Onboarding Wizard, and questions in this section cannot be set to mandatory.

However, these questions can be disabled, and instead you could create a custom questionnaire step, add the questions there, and set those questions to be mandatory instead.

Before doing this, please test that this works in the way that you envision using a test programme, and a test learner.