The simplest way to own all of the Brookfield subsidiaries are to just own Foundational Stock Brookfield Corporation (TSE:BN).
When you start getting into the subsidiaries, you are primarily doing so because you want individual exposure to that segment of the company. For example, owning BIP would give you exposure to the infrastructure portion of the business. Pipelines, etc. If you own BEP.UN, you'd own direct exposure to the renewable portion of the business. BAM the asset management portion.
When you own Brookfield Corporation, you own all of these, plus exposure to the insurance side of things.
Direct exposure to the entire conglomerate = Buy Brookfield Corporation (TSE:BN)
Direct exposure to the subsidiaries to get exposure to a particular sector = BEP.UN, BIP.UN, BAM.TO, etc.