Looks like they are NOT playing AGAIN.
When did they last play doubles at a slam??? Wimby 2002???
With a few exceptions, they should look back and notice that when they played doubles, one of the sisters won the slam. And... Most of the time won the doubles also!!
Exceptions: Three times, Serena won the slam without doubles. RG 2002, Wimby 2003, and AO 2005. In 2001 at the AO, V&S won the doubles while Jennifer won the title.
V & S, if you want to win slams, play doubles!! It is much better than practice.