Nofollow for multiple sites owned by the same parent company?

[rclark85]

Hi guys - first time posting here so hope this is enough info! I have a client who has multiple domains for legitimately different businesses and or login purposes to their products. They are however 'owned/operated by' the same overarching company. The different sites have links back to the overarching company site within, for example, the footer of their site on the logo. e.g. "Part of Company X" which then links back to the site.

What I'm unclear of is whether these links back to the 'parent company' site should have a 'no-follow' associated with it or is that just a bit of a positive for the client that they have lots of different domains that are powered by them and can therefore benefit from the backlinks?