There’s no reason for those single quotation marks to be around the word weakest; get rid of them.
Add a comma after bloodline.
I know what the latter part of the sentence is trying to say, but what it actually says is something else. What it says is that your powers are more subdued than your family, and what it wants to say is that your powers are more subdued than your family’s powers. See the difference? Adding those of is the least invasive way to correct the sentence.
You’re the weakest member of your bloodline, and as a result, your powers are more subdued than those of the rest of your family.
I think subdued isn’t the right word here (I don’t trust this writer to know what it means and to use it correctly), but I don’t have a suitable replacement at the moment. Subtle, perhaps? That’s if the powers are merely less obvious rather than actually weaker.