Lois’s answer to “I'm a sci-fi romance author with my debut coming out in July. I've seen your name come up often as …” > Likes and Comments

Many Anne McCaffrey books have romance in them and she started writing in the 60's. So she might be considered a founding author of sci-fi romance.
Unless you consider Frankenstein's monsters' wish for a partner to be romance then it goes way back to Mary Shelley.

Thank you so much for answering! I love the idea of a "romance spine."