I was asked by my daughter's ex if I would mind if he asked her. We happened to be standing together in a queue at the time, and Daughter and husband were waiting for us at the table. He caught my husband separately later that day, and spoke to him.
I liked that he thought my opinion was as important as Husband's, but hadn't expected either of us to be asked. I'm sure he would have asked her regardless of our responses, but wanted to be sure he would be welcomed into the family. It had absolutely nothing to do with ownership - what a preposterous idea. My daughter, rightly, was always going to do what was right for her in such matters, as did I. It was about recognising that marriage is about joining an existing family as well as creating a new one, and I thought it was a nice touch.
As it was, she didn't want to marry him and they broke up a year or two later.