Why not? I've borrowed thousands of dollars from family at times, lent thousands of dollars to them at others, and we've always repaid each other eventually.

It's normal to forgive a loan to family if circumstances change, or to give money no-strings-attached if they need it, but it's equally normal to loan money to help with cash flow problems and then expect repayment eventually.

>I've borrowed thousands of dollars from family at times

Is this common? Such a thing is unthinkable to me, and even friends from more businesslike families than mine have expressed major shame to me that they had to get a couple grand from their dad to cover closing costs (paid back within weeks)

Really? In my experience people pay back. When I was a student I and my friends ofent had to cover each other when buying tickets or whatever.