Pinned straw:
RDG is considered to be a subsidiary - i.e. a controlled entity - of MinRes @edgescape because MinRes own 64.31% of RDG's SOI. There are no other "Subs" for RDG other than MIN.
Whenever MIN lodge a change of interest of substantial holder notice for any of the companies they hold 5% or more of, they have to list all of their subsidiary companies, and as I remarked here recently, that list goes to over 100 companies / entities, and takes 5 or 6 pages, and always includes RDG, so that's another reason why the RDG share price has reduced, as it's just another related-party set-up that in this case looks after Chris' brother Andrew Ellison (RDG's MD) and keeps him in the money.
I note the Chairman of RDG's 3 member Board is Mark Wilson, who also happens to be the CFO and Company Secretary of MIN. Then there's Andrew Ellison, the MD (& Chris' brother). The third and final RDG Board member is Mike Grey, who happens to be Chief Executive, Mining Services, at MinRes - see here: https://www.mineralresources.com.au/about-us/leadership/mike-grey/
Looked into them, won't touch the company. Either company now. RDG will live or die based on the whims of MinRes, and everything has shifted somewhat recently, so where that leaves RDG I do not know, and don't much care, but I daresay they are NOT any better off than before all this blew up.
The RDG business comprises mining services and project ownership, like a real little mini-me version of MinRes - like, REAL little. The mining services appears to mostly be engineering and construction services for MinRes these days, big surprise! - and RDG also have something called the Lucky Bay Garnet Project, around 35km south of Kalbarri in WA, which they described in their annual report as having "experienced plant performance issues". It's likely a nearology play, being a little north of GMA Garnet Group’s existing garnet operation, which is the world’s largest supplier of high-quality alluvial garnet and has been in operation for the past 40 years.
RDG have some other irons in the fire, but nothing that makes any money outside of mining services - specifically structural and civil engineering and construction for miners - and for themselves also - from what I can see from a very quick skim through their recent reports.
MIN did own 75% of RDG, now diluted to 64.31% due to RDG issuing more shares, some of those possibly to Andrew Ellison who as MD of RDG owns 141,333,058 (141.3 million) RDG shares plus another 5,131,357 (5.1m) options.
Source: Resource Development Group (RDG) 2024 Annual Report
https://resdevgroup.com.au/investor-relations/ [what they do]