在一起一年半的英文文案可以表达为 "Together for a year and a half" 或者 "We have been together for one and a half years"。

如果需要更富有情感的表达，可以考虑以下几种说法：

1. "Our love has blossomed over the past year and a half, growing stronger with each passing day."

2. "It's been a year and a half since we first met, and our bond continues to deepen with every moment we share."

3. "Through thick and thin, we've been together for a year and a half, and I wouldn't trade it for anything in the world."

4. "Our journey together has been filled with joy and challenges, and I'm grateful to have you by my side for this past year and a half."

5. "One and a half years ago, we embarked on this incredible journey together, and I can't wait to see what the future holds for us."