There are basically just 3 plot lines to a story: 1) person against person 2 ) person against the environment 3 ) person against himself. (Longer stories have more than one plot line) And there are just 3 settings: past, present or future ( far back, middle ages, the roarin' 20's, etc.)
A place would help....desert, jungle, city, suburb, farm, moon, etc.
A romantic story will have two people....or an animal, such as a faithful dog, penquin, dolphin, etc.
The play called "The Fantastics" breaks romantic plots down into easy parts. Innocence, puppy love, fall from innocence, sacrifice, forgiveness and reuniting.
The characters may be fanciful or taken from real life and given scripted roles.
The lovers may come from diverse or similar backgrounds. Diverse is easier because conflicts are easier to see.
Make a few of these decisions and a plot may come to you.