Their Sweetheart City Love (Colorado City Series Book 2) by Emilee Harris

I like stories of older couples falling in love, but this is about a couple already in love. Twenty-six years ago, their lives took different directions, and they meet again when her adopted son and his daughter meet and fall in love. There are secrets Lucy kept from Rick, because of the royal life he was living and she was just a woman running a boarding house in Denver. The fire when these two come together is always there, even when Lucy is already engaged to Archie Stanton. The interaction between these two is passionate, and even when they are angry with each other, they are caring about how the other is perceived.