When DH and I bought our house, my DF gave us some money. DM, who had recently inherited a little money from my DGM, said she wanted to loan us 10k from her own money. Then, when I tried to pay her, she refused to take it back!
I recall one time when we (after we were married DH and I) were living with my parents while I was in law school. I had about 10k in DF's closet for tuition. He asked me if he could borrow it for taxes and I said sure. Didn't think about it again until it was time to may the next tuition payment and he gave me a check. If I didn't have to make a tuition payment, I would not have mentioned it. DF gave A LOT to my family. I had to put the brakes on his generosity a few times.
With kids I tend to gift, not loan. Although my oldest did call from the vet's office for an emergency "loan." Never saw that $ again, although the rest of my kiddos are pretty responsible financially.