We know Blackbeard is the son of xebec and shares his lineage with Davy Jones but that doesn’t necessarily make him the true successor of their will
We know will is more than just about being blood related the best and most obvious example being Luffy. Luffy being the one to share dreams with Roger and succeed joyboy. It not being Roger’s blood son Ace or adopted son Shanks
Point is same way Ace and shanks might not have been the true holders of their will it could apply to Blackbeard
We know xebec was basically his equivalent to shanks for so him being the one to really surpass them could be interesting