Unless they ask you for help with this and (most importantly) are willing to follow through on setting limits with the "moochers" in their lives, there is not much you can do. You can lend a sympathetic ear from time to time and say something like, "It's tough to hear your struggles; is there anything I can do to help?" and leave it at that. Based on what you are reporting, they are competent in the eyes of the law and are doing this of their own free will, so interventions on your behalf may not be very productive.