He was on extremely bad terms with Tadatsune SHIMAZU, and received a letter from Iehisa questioning his actions saying 'family heads that do not treat their vassals with consideration lack the credentials to lead,' but it lacked persuasion because Iehisa himself frequently purged his vassals.
島津忠恒とはきわめて不仲であり、家久から「家臣を大事にしない当主は上に立つ資格がない」という内容の詰問状を送られているが、家久自身が家臣の粛清をたびたび行っており、説得力はなかったようである。