Romantic love is as old as humanity
To begin with, sex with love is a recent historical invention only made possible by the medieval Courtly Love Tradition and the increase in literacy that propagated it.
You know, I'm no historical expert, but I don't think that's true. Homer's work would be a lot different if love hadn't figured into it. Odysseus and Penelope? If that's not love, what is? The traditions and her own self-interest demanded Penelope remarry. Did she?
Certainly the Old Testament is studded with love stories.
Then there's this:
To hear your voice is pomegranate wine to me:
I draw life from hearing it.
Could I see you with every glance,
It would be better for me
Than to eat or to drink.
-- Love poem found from ancient Egypt, circa New Kingdom
Maybe I'm missing the specific definition you're using, but my view is that humans were holding hands pretty much the moment they stopped walking on them.