!!! your so clever!!!

BUT i highly doubt its Regulas.

I read in an interview with JKR that a question was asked "Are any future books going to include Sirius's brother Regulas, or will we hear from him" and JKR answered with a dick answer "Well seeing how Regulas isnt exactly alive, hes been quiet lately" or something like that.

But JKR has always had the technique to fool and awe the ones who least expect it.....