"依赖其供养的子女" can be translated into English as "children who are financially dependent on them" or "children who rely on them for support". Here, "them" refers to the parents or guardians who are providing the financial support.
For a more context-specific or formal translation, you might also use phrases like "children dependent on their parents'/guardians' financial support" or "children who are financially reliant on their parents/guardians".