To work on love in general, Duchess Gremory helps well. King Beleth is one of the best in there, if I don’t say foolishness, but he isn’t very convenient. The Duke Dantalion and Sitri can also help you, but on other aspect of love. Here’s another post that can help you :
And then you can enter into communication with spirits / entity other than Grand Dukes or Duchess. Vampires are good at it, they are romantic beings after all