Family of a British Citizen

[WMalik80]

Dear Forum Members,
I am after some valuable advice from experienced members. Apologies if similar sort of scenario has been asked before but I have searched the forum and I could not find any similar situation.
A friend of mine is in the following scenario,
A British Citizen (Became citizen through Tier 1 General route) intends to apply settlement for his family abroad. There are 4 family members, a wife and 3 children (an adult - over 18 years and two under 18). His family has never visited UK.
Questions
• Can children apply for settlement or they have to go through 5 years long dependent route?
• What will be the route for adult dependent child?

I would appreciate if you can give me some valuable comments on above.
Many Thanks in advance.