Thanks for your question.
They would not qualify for UK citizenship in those circumstances.
Their ILR would have been revoked given the amount of time they have been outside of the UK unfortunately.
As such they will have to apply for Returning Residents visas before they travel. In normal circumstances a person can only apply for this if they have only been absent for two years. However, a person can apply after being outside the UK for longer than 2 years if they can show that they either have strong family ties with the UK, or have lived in the UK for most of their life.
If you are to all return to the UK then this would be sufficient to demonstrate your family ties to the UK but you will have to show the UKBA that you all intend to return by producings statements confirming your plans to come back to the UK. Their previous period of residency will also help to an extent.
All the information confirming the above and how they can apply for this is contained on the following page:-
I should think they will be fine but it takes quite a long time to determine an application so you should allow at least three months before submitting the application.
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