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.