MOFU  definition will be changing on 19 November 2016. Currently it is possible to include in some visa application dependent relatives other then children and partners – for egzample parents 

These new arrangements will impact all applications lodged on or after 19 November 2016 (applications lodged prior to this date must still be assessed against the existing requirements).
The two key differences from current arrangements are: only partners and children can meet the definition (other relatives are no longer permitted);  ‘children’ are limited to individuals aged: · under 18; or · between 18 and 23 only if they are dependent (an upper age limit has been added); or · 23 or older only if they are physically or mentally incapacitated for work