Companies within a group of companies are not generally privileged. Each company is regarded a separate entity.
The forwarding of data from one company to another within a group of companies qualifies as transfer of data to the effect that the general restrictions on data processing apply. The exemption based on the processing entity’s legitimate interest is often referred to for justification.
In these cases, however, the legitimate interest needs to be demonstrated for every individual transfer. If, for instance, the transfer of data in an anonymized form had served in the purpose equally, the transfer of personal data may no longer be covered by the legitimate interest.
Also, when relying on the exemption based on legitimate interest, such interest has to prevail the data subject’s privacy interest.