When someone is responsible for another person or thing, we often say that they are "in someone's charge." But there are many other ways to express this idea. For example, you might say that the person is under their care, supervision, or guardianship. If you're talking about a possession, you could say that it's in their possession, custody, or safekeeping. Another option is to use phrases like "in someone's care," "under someone's watch," or "within someone's responsibility." Regardless of which synonym you choose, the underlying meaning is the same: someone is responsible for the well-being and safety of someone or something else.