AKA: Hikaru Genji Plan.

You fall in love with a woman, having adopted her and raised her from childhood. She looks up to you, thinks of you as a father figure or beloved uncle (no blood-relation) a guardian, counts on you to be there when she needs you etc. She may have even vowed to marry you when she came of age. Then, when She Is All Grown Up, she decides she is in love with you, or you with her, or both...

"I'm just waiting for my wife to grow up." — Grover Cleveland