These dramas have so similar vibe. Both are melodramas, telling about people who fall in love, for some reason can't be together, but fate won't keep them apart.
Both have iconic time skip, which is very important for the plot - first few episodes are about teenegers, and next, longer part is about couple in their 20thies. In Love Rain, second part is focused on previous character's children, while WISFC focuses on the same pair, but after time skip.
Still, in both dramas not only children, but also parents of them fall in love with each other (they live in unhappy marriages).
Those are melodramas at its finest, so please bare in mind that it may be hard to watch because of its overwhelming so-called sadness. Not to mention that topics such as death and sacrifice happiness are present. Forbidden love is the most important theme though.
Definitely worth giving a try if you like The Bold and the Beautifull melodramatic vibe.