Thanks for your question. I will try to help.
Obviously with Brexit looming the situation is a little different than it would normally be.
However, your friend would have to apply for an EEA Family Permit for both him and the child (if the child is not a French Citizen) in order to travel to the United Kingdom with the wife with a view to staying here permanently.
The link for a family permit is here:
Then if they arrive in the United Kingdom before March 2019 then he will have to apply for an EEA Residence Card in order to confirm his right to be in the United Kingdom and working:
If they arrive in the United Kingdom just a short while before March 2019 or they arrive before March 2019 and stay here past March 2019 then he will have to apply for pre-settled status which is the application which people need to make following Brexit. This would allow him to stay in the United Kingdom for 5 years with his wife and ultimately then apply for a permanent right to stay in the United Kingdom.
The French Citizen wife can travel here at the moment on her French passport without restriction. However, once she is in the United Kingdom she will also need to make an application after March 2019 to the Home Office for pre-settled status which again is the application type needed for EEA citizens staying in the United Kingdom past Brexit. The link to applications for pre-settled status is contained here:
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