the secret keepers

the secret keepers
Is there a reason why the Potters could not be their Secret Keeper?

In Harry Potter, Sirius Potter is back for their family secret-Keeper to protect their position, then they should go to Pierre Pettigrew. My question is, why not just use it yourself? Would not been much safer?

I'm only guessing here, but I think they need to be a secret keeper, which is ( their friends or if Wormtail their enemies) know where they are, but only the secret keeper can say that because others can not because of the magic. I think people can not have their secret keeper, who had that JK has written books. Sorry, I am not so useful, but it is my own theory. Mv as I said its a plot hole, even the best writers sometimes

The Secret Keepers (Part One)