United Kingdom, Dec. 24 -- Serena Williams has gushed over her sister Venus Williams after watching her sibling get married.

The 44-year-old former professional tennis player has hailed Venus as her "protector" and "teacher" after the fellow ex-tennis pro, 45, wed actor Andrea Preti, 37.

Serena wrote on Instagram: "My sister's keeper. Venus, where do I even begin? From the backyard courts to the biggest stages in the world, you've always led with grace, strength, and a heart bigger than any trophy. Watching you step into this next chapter surrounded by love felt like watching the sun rise...steady, powerful, and full of promise.

"You've been my built-in best friend, my protector, my teacher, and my reminder to always walk in purpose. S...