They've played each other in four Wimbledon singles finals, and won six titles in doubles alongside each other at the All-England Club - so Serena Williams isn't used to being without her sister Venus during the London fortnight.
The pregnant Australian Open champion joined ESPN’s SC6 with Michael and Jemele live on Thursday to talk a little bit about what it's been like to watch her sister run through the draw at the All-England Club - as she'll face Garbiñe Muguruza on Saturday in the ladies' championship with her sixth title on the line.
"I feel like I'm there, in a weird way. I feel like I've been there for the whole journey," Serena said. "We talk every day and we text every day, not about tennis always - our relationship isn't based around tennis so it's just been really great. I miss her a lot and I look forward to her coming back.
"...All my energy is towards making her want to be great and making her want to win. It's just a totally different feeling."
Watch the full interview clip below!