What's the best way to maintain design consistency across drastically different platforms?

We're launching a new product that will have a web application, an iOS app, and an Android app. I'm finding it incredibly challenging to keep the design visually consistent across all three without making one feel out of place or losing our unique brand identity. How do you seasoned designers approach this balancing act? Any strategies or tools that have genuinely helped you bridge this gap would be amazing to hear!