The Longbottom's Secret Keeper

[dj_bagshaw]

No: HPFGUIDX 86613

I just re read Book 6 again, and got to wondering something...

I am assuming that the Longbottoms must have had a secret keeper, 
just as the Potters did.  If both families fit the constraints of the 
prophecy, this would only make sense...

Why, therefore, were the Longbottoms found and tortured by death 
eaters?  Who was their secret keeper and why were they betrayed?  If 
the Longbottoms did not have a secret keeper, why not?  Didn't 
Dumbledore warn that family too?

Any suggestions or references to past posts would be helpful.

~Kate