The family members of EU citizens have more rights in the UK than those of British citizens. They can move to live in the UK, even if they are not EU citizens themselves, and automatically have right to reside so they can apply for benefits, social housing, etc.
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Non-UK family members of British citizens cannot do that. The laws and rules in the UK should not be less favourable to family members of British citizens. Close family members of British citizens have to apply and pay for visitor's visas when they wish to visit their family in the UK, but family members of EU citizens can settle in the UK without any charge or proof of being able to support themselves once they are here.