Domain is trying to replicate with sibling child domain and root domain

I have a root domain (call it a) and two child domains (call them dev.a and services.a) (fqdn is a.s.local but I'm abbreviating).

dev.a is a single domain with 2 DCs. However, if I go to Active Directory Sites and Services, it has all the domains in the entire forest from the root domain and including all child domains. Is this correct?

In addition, if I do repadmin /replsum, the domain is trying to replicate with services.a and a (the root domain). It should only be replicating within itself.

I've read that to remove additional domain controllers not needed from sites and services is to do metadata cleanup or expand these DCs from sites and services, right click NTDS Settings and then delete (which basically brings up the warning about deleting metadata). However, these DCs are still functional and must not be decommissioned completely (if this is what happens). I just need to remove from them from the topology - how can I do this?

Thanks