Scenario 1: Grandfather loans money to Grandson to buy a vehicle. On paper the math works in that he is getting a better rate than the savings account and giving Grandson a better rate than he would get from the bank.
Fast forward: Grandson for whatever reason (loss of job, loss of interest, wrecks it, etc) stops making the payments. Grandfather approaches Grandson. Get's blown off and/or played for sympathy. Still no payments. Grandfather approaches Grandson's parents . . . who get mad at son and things escalate from there. You can add may different threads this one could take and none of them are good.
Scenario 2: Dad/Mom decide to loan the kids some money for a down payment. Kids take it, all is well and paying on time. Thanksgiving rolls around and the kids start talking about a cruise they are going on. Mom shoots a sideways glance. Maybe even jokes about the money being owed.
Long story short: The family dynamic has been changed by money. Why do this to you and yours. Oh and the kids . . . immediately took on more jobs, sold stuff, etc, to pay Mom and Dad back. This way Thanksgiving Dinner tastes the way it should in the future.
Scenario 3: Friend/Family turned down by the bank for a loan due to a myriad of reasons, or just one big one, that makes them a high risk lender. That is right. Turned down by the store that sells money. Turned down by the place that will bend over to get a loan in place because this is how they make their money. Even they could not figure out how to take on this risk.
They come to you, you loan the money. What makes you smarter than the bank? The risk never went anywhere.
One cannot borrow their way out of a problem, nor to prosperity. Do not inject money into family or friend relationships. If they need money, and you want them to have it, give it to them.