This page explains the circumstances in which you can apply for permission to stay here as the dependant of someone who is already here in the investor category (Tier 1 Investor) without having to leave the United Kingdom and apply for entry clearance (permission to come to the United Kingdom).
You can apply for permission to stay here as the dependant of an investor without having to leave the United Kingdom and apply for entry clearance. This is if your last grant of entry clearance or permission to stay here was as the partner or child of a person who has valid leave to enter or leave to remain as an investor, or who is at the same time being granted leave to enter or leave to remain as an investor.