Highly unlikely that he will be approved for citizenship unless one of his parents apply at the same time or before you apply for him. It would be very different if he was born in the UK.
Children born abroad to parents who are applying for British citizenship
Where one or both parents are applying for British citizenship they may apply for one or
more children who are not automatically British at birth (see “Automatic acquisition of
British citizenship” above) to be registered as British citizens as part of a “family
application”.
Children in this category will be considered at the Home Secretary’s discretion and will
usually be registered only if both the parents are granted or already hold British citizenship,
or if one parent holds British citizenship and the other is settled in the UK
Page 13 of the MN1 guide, link below
http://www.ukba.homeoffice.gov.uk/sitec ... de_mn1.pdf