Here is a warm, sincere, and cringe-free toast that clocks in at around 45–50 seconds (about 130 words). 

It focuses on the genuine core of climbing—trust and partnership—rather than forcing cheesy rock-climbing puns.

***

"Hi everyone, I’m [Your Name], [Sister's Name]’s [brother/sister]. 

If you know my sister, you know she loves to climb. And the thing about climbing is that it all comes down to trust. You have to know, without a doubt, that the person on the other end of the rope has your back. 

When she met Elliot at the climbing gym, she found exactly that. It was clear pretty quickly that Elliot wasn’t just a great climbing partner, but the perfect life partner. Watching the two of them together, you can see how much they trust and support each other. They just make a great team. 

Elliot, welcome to the family. We’re really glad it was you holding the rope. 

Everybody, please raise your glasses to [Sister's Name] and Elliot. Here’s to a lifetime of supporting each other. Cheers!"

***

**Pro-tip for delivery:** Speak a little slower than you think you should, and take a brief pause before the paragraph about Elliot. It makes the words feel much more natural and impactful!