Based on best practice, each repo will have its own stage.

repo1 -> dev_stage_01
repo2 -> dev_stage_02

This avoids the deletion and recreation of the common single stage (eg:- dev) reference when any one of the repos are getting deployed to the common single stage(dev).

While mapping these to Api Gateway Custom Domain, there will be multiple entries.

API             Stage           Path
api_gatewaay -> dev_stage_01 -> /
api_gatewaay -> dev_stage_02 -> /