will you marry me?

Last night Ellie and Will were sitting on the couch. Ellie asked Will "When we grow up, will you marry me?". Will didn't respond and Ellie didn't seem to mind. As I was putting Ellie to bed later, she informed me that she wants to marry Will when they grow up. I tried to explain that you don't marry your brother. Ellie became quite upset. So I tried for the simpler approach. I asked "Why do you want to marry Will?" Ellie simply stated "because I love him"