From the way you write, I assume you are from London or the South East, it has a typical London lilt to it. Now I take it that the incidences in Blackpool are what your brother or sister told you. Your local police won't do anything about that because that is hearsay. So you will have let the people in Blackpool deal with those things.
Now you don't say when or over what period of time your family members were murdered. If they lived in the East End, they may have been in contact with some pretty mean characters.
You seem to imply that you actually know or suspect who the culprit is. You know who is doing these things. Either that, or you want to shop someone or at least ruin there reputation.
I can have my suspicions of what you are trying to say, but really it is up to you, to name, shame, and prove it.
In the UK it is very difficult to get a conviction against a rapist, and your best chance is to go right away, so that DNA of the rapist can be collected.
However, counselling should be available in your local area, and the Citizen's Advice Bureau should be able to put you in touch with a counsellor. The counsellor won't do anything about the justice of the case. She won't help you to get back at him, but she will help you to sort things out so that it does not blight every aspect of your life.