Suppose you have two wizard scions, and each of them establishes a level-4 source holding in a swamp with 0 population and 8 max potential source.

Can both of them increase their source by the rule action so that both of them have level-8 connections to the source? Or is there a limit -- if one of them gets level-5 connection, does the other one have to settle for level-3?

I know that holdings can be contested, but I'm not clear on how the rules work. The rulebooks don't have many examples.

Thanks.