As to how this whole thing transpired.... obviously, this was not a spontaneous proposal. A lot of planning went into this "moment". Without going into a lot of details, I'll just say this family is quite unique in a good way. He wanted his family and hers to be part of this milestone in his life. His girlfriend was the only one who didn't know exactly what was going to happen. The exact moment was a private one. We, the photographers, were hiding in open. We were careful as to not to ruin the moment. It worked as she didn't even realize we were there until he told her... oh, by the way.... It was obvious that she didn't mind.

No, it's not a localized custom. It's just a unique family doing things in their own way.
We did have a contingency plan just in case she didn't say yes....