It's Mother's Day in much of the world this weekend - and that means WTA stars are paying tribute to their own moms, or enjoying time with their children.

Ana Ivanovic is heading out to explore with her little ones - and Petra Kvitova is doing the same with her niece and nephew.

Caroline Wozniacki basks in the sun...

...but the heat is making Sabine Lisicki's workout pretty tough.

And Kristina Mladenovic and Caty McNally had good reasons to smile.

Sports leagues unite for The Real Heroes Project