Reading these suggestions, I'm realizing the books we're naming aren't 'love stories' in the genre sense; they're life stories where love is the key ingredient. That's probably the best way to find them. Don't search for 'Tamil love story married couple'. Search for 'Tamil family saga', 'Tamil literary fiction', 'Tamil stories about middle age'. The love will be there, woven into the fabric, often more realistically and movingly because it isn't the sole, glittering focus. It's just there, like the furniture, worn in and essential to the structure of the characters' lives. The emotional journey is the life lived together.