Or is that a different trope?
Topic on Talk:I Want to Bear His Children
95 percent of the time, they are associated. Because marriage is often intrinsically linked to reproduction, as "spreading this qualities through future generations" or simply "I want your traits to spread through my family".
And the "proper" way of doing it is through marriage.
However, this trope isn't about reproduction. It's about a stock phrase.
"Marry me!" is Engaging Conversation.