I would suggest breaking down the peoblem (lack of first hand experience) into two parts.
First, let's tackle emotional bonds. Surely you have experienced this. So try to write short shortstories whose aim is to shine a light, so to say, on emotional bonds. Write about the bonds between siblings or parents-children. Write about one's emotional attachment to a beloved toy, pet, place and videogame.
Remember that the objective is to focus on the strength of the emotion, no matter what type. Feel the sadness of losing someone or something beloved, of meeting them again, the excitement that makes one not be able to focus on anything else.
Before you finish this step, write a few scenes that focus on addictions. Have you ever become addicted, say, to candy crush? Those feelings of pure pleasure when you get to play, the fidgetness of when tries to avoid and the guilty pleasure of managing to play it in a forbidden place (like work, the classroom or a boring family dinner). That's what you need to capture in your writing.
Now that you've focused on general emotional bonds, it's time for the next move.
Romantic attachments are bonds like any other, but the object of their attention is another human being. You'll need to add a good level of addiction (being in love is one of the strongest addictions I know, drugs aside) and base it on the strongest emotional bond you've ever felt for someone.
Next, you do some reasearch. Find descriptions of being in love, whether you get them from family members, friends, magazines or the internet. Try to base this research on real people!
Now you can write again. Do not write a full fledged tale but short shortstories. Focus on little things of the romance: the excitement of the first meeting, the routine of waking up every morning next to the person you love, etc.
Once you have managed to capture different shades of a romantic bond and you feel you understand its strength, then you can write a romantic novel.
More than plot, is the feeling that will make it feel true and original.