I posted an answer here to Should I charge my children interest when they borrow money?
The answer was live for a couple days but I see that a moderator has deleted it. I am confident that I appropriately answered the question, and so if possible, I would like for this answer to be undeleted.
Below is my deleted answer to Should I charge...money?
Ultimately for me, the answer to this question is pretty much a "no", but keep reading anyways. The following are passages from the Bible (nasb version).
here is an excerpt from Deuteronomy 23:
You shall not charge interest to your countrymen: interest on money, food, or anything that may be loaned at interest. You may charge interest to a foreigner, but to your countrymen you shall not charge interest, so that the LORD your God may bless you in all that you undertake in the land which you are about to enter to possess.
From Exodus 22, it specifies "to the poor among you":
If you lend money to My people, to the poor among you, you are not to act as a creditor to him; you shall not charge him interest.
There are also many quotes from the New Testament that encourage more kinds of "selfless" giving. For example, from Matthew:
Give to him who asks of you, and do not turn away from him who wants to borrow from you.
Based on these passages I would suggest that you try to inform your kids about the rules of your loans. If they aren't paying them back because they have a habit of mismanaging their money, or are lazy, then perhaps you don't offer them any more money until they pay their first debt back.
But if their neediness isn't necessarily their fault, or they sincerely apologize, then perhaps you give them a loan.
Yet in either of these circumstances, it doesn't really make sense to charge interest on a new loan. In the first example, if you can't get your previous debt paid for, then just "charging interest" doesn't seem to help the situation.
But if there's anything to garner from this discussion, it's that generosity (and forgiveness) are important.