My parents gave me money when I needed a little help when I was in my early 20’s. It wasn’t a loan, but it wasn’t a lot. $1,000 one time, and then also birthday and Chanukah money, usually $500 each. Also, when they visit me they pay for food and give me some extra money. If I needed to borrow a large sum I can’t imagine they would charge me interest if they even expected me to pay it back.
My husband and I loaned money to his brother and brother’s husband at one point. We did draw up a one page contract with the amount and how much they would pay us every month. It was several thousand. No interest was charged. When I helped my sister with some money I just gave it to her, it was only $1k, no words about paying me back, I was fine if she never did. She did pay me back eventually, but that was completely on her own.
If I had kids I would give them money to make their life easier and to have fun as long as they were making an effort to support themselves and not being entitled. That’s assuming I had the luxury of feeling financially secure and had extra to give.
Parents who have more money than they need I think should start giving the money to their kids earlier rather than later. Waiting till you die doesn’t really help your kids the same way money at a younger does if spent or invested well. Plus, there are tax loopholes for gifting money.