Come to think of it, I vaguely remember Blackbeard and Cerberus comparisons...can't remember where or why though.
I did a little research on that thought and I found a theory that suggests that Black Bear had a zoan type devil fruit ability previous to his yami yami no mi fruit. So this allowed him to have three heads which meant three different people, the main point they make is the three skulled jolly roger, but the other point is pretty interesting.
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In Chapter 434 of the One Piece Manga, yonko Shanks ends up going aboard Whitebeard's ship to warn Whitebeard about the danger that Marshall D. Teach (Blackbeard) could potentially cause. Then he explains that he got that scar on his left eye from Teach. Now immediately you might think that he used the claw weapon that Teach had to give Shanks that scar, but that's not the case at all.
In this pic you can easily see that his weapon has four claws, but shanks has 3 scars on his left eye, and since Oda doesn't do this shyt on accident, we can assume that he has a three-clawed paw. Plus the whole zoan-type thing makes sense since he already has a paramecia and a logia type fruit, he'd have all three types of devil fruits, not to mention arguably two of the strongest logia and paramecia types. Plus if the whole cerebus zoan type is a mythical and a strong one it could arguably be the strongest zoan-type devil fruit. Blackbeard planned all this shyt from the beginning to have the strongest zoan, logia, and paramecia types.