My husband always feels the need to jump everytime his family needs anything?

My husband comes from a fairly large family consisting of a brother and 3 sisters which all work, grown and married with children between the ages of 7-20 My mother in law also works a decent job but between her and one of his sisters they always call my husband asking to borrow money and it's always large amounts. The sister always pays it back but I feel that they are taking advantage of my husbands kindness. He gave his mom a fairly new car that he paid off because he purchased a new car. Instead she was ungrateful and said she wanted a new car and here she didn't have to worry about a car note. As if this wasn't enough she loans the car out to the sisters husband who tore up her previous car so this left her with no transportation which is why my husband gave his mom the truck to use, then the sisters husband tears up my husbands car that he let her use and totals it out. The vehicle still had my husbands name on it and I felt it was disrespectful that she would loan the car out knowing it wasn't hers to have but to use. She now thinks that she will get the insurance to buy another car. I also feel like he doesn't know how to tell them NO. Whenever they call he always has to run over there and if we have plans they seem to get changed. Holidays are always with them, they never seem to spend it with their inlaws and they are married but I go and spend it with my family anyway because I feel like I am always with his.