(CNN) -- At times it was almost painful to watch. At one end of the court the world's No. 1 female tennis star playing well within herself; at the other her sister, a long way away from regaining that form and status.

"Venus has had a great week, and honestly, if she hadn't had to play so many matches, it would have been a much tougher match," Serena Williams said after comfortably beating her older sibling on Saturday to reach the final of the Family Circle Cup in Charleston.

The 31-year-old was slightly overstating the rigors of the competition in South Carolina, a tournament that heralded the formation of the women's tour back in 1973 but has this week attracted just two of the world's top-10 players.

Serena is one, and the other -- 10th-ranked Caroline Wozniacki -- crashed out in the quarterfinals on Friday against Swiss No. 63 Stefanie Vogele.

Both Williams sisters won two matches on Friday to set up their first meeting since 2009, but it was defending champion Serena who looked the least affected as she won 6-1 6-2 in just 54 minutes.

"She'll never admit it, but I don't think she was 100%," Serena said of her sister, who was diagnosed with a debilitating autoimmune disease before the 2011 U.S. Open -- a grand slam she has won twice, along with her five Wimbledons.

"But you will never get that out of her. And quite frankly, three matches for her is much tougher than three matches for me. It's definitely not easy -- because I'm struggling, and I can't imagine what she must be feeling."

Answer the following questions:
1. Who is this about?
2. Where were they?
3. What were they doing?
4. How old is Serena?
5. Is she the older of the two?

Numbered answers:
1. Both Williams sisters
2. Charleston
3. Playing tennis
4. 31-year-old
5. yes