>>282023581
We already know Blackbeard has two sisters. We have known that for a long time now.

>>281443657
It's an unused concept published in a magazine alongside concept art of Blackbeard having two sisters (Ace would have met them and been flustered at how nice they were).
It's likely these were all scrapped since they were revealed this way and the sisters subplot obviously didn't happen, but you never know if Oda might reuse them in some way later down the line. I think Blackbeard's jolly roger is more suspicious with this stuff.

Reminder
BB have 2 other sister

>>280345552
There's actually concept art for Blackbeard's mother (and two sisters), but since it was released and the sisters part was probably scrapped it might not have any bearing on the final story unless you believe the theory that he shares his body with the souls of his sisters which is where "It's not him, it's them" comes from, part of why he can eat multiple DFs, and why his jolly roger has three skulls.