Citizenship for sons born abroad

[fathid]

Hi My friends two sons were born abroad before hi naturalisation, He was naturalised British citizen other than by decent in 2009. his sons were born abroad in 2005 and 2008. the father and sons living abroad and wanting to come to settle in UK. what does he need to do can he register them as British citizens by decent following section 3(2) of 1981 immigration act of they are not entitled to.
your help is very much appreciated

[CR001]

Section 3(2) registration is not relevant to your friends circumstances.

Children will need a child Settlment visa.

Where is the other parent and is the other parent also coming to the UK?