Two Seperate Internal Networks: Is there any way to link to share resources?

(re-uploaded because i meant to crosspost whoops)

Hi all, I'm currently in the process of trying to set up a homelab/SoHo network for personal use but also so that my roommates can share resources seamlessly and without the internet.

Unfortunately, the network as it is currently implemented used two different routers from two different ISPs, effectively segmenting off the network into two very distinct LANs.

Is there any way to get these networks to talk to each other for use in sharing resources? I have 2 spare workstation units (one of which is reserved for the homelab itself) and the goal is to set it up for mainly NAS/media streaming inside the 'merged' network.