If wife or any other dependent is accompanying you, only then you need to fill in their details
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For e.g., I'm applying for Canadian skilled immigration. But my wife is not accompanying me (I need to go there alone, settle, get a job, have something in my pocket before bringing her or my child to Canada), then in my case, I would not need to add her details in my EE profile, other than the fact that I'm married.
But, if my wife or my dependent child was accompanying me to Canada, I would need to add her's and/or my child's details in my EE profile.