Sorry I should have posted a Hello to everyone before I made a post. I hope to learn a lot from your site....it's about time I got myself sorted out

Hi My sister received a letter from J2 solutions at her home address. Well it was address to the occupier. Looking for information about myself at my previous address. My sister did not contact them. It states on the letter that any information she can give to where I am now living will be treated in strict confidence. Is that legal? How did they get her address? I have her address as a fowarding address for my mail but this wasn't forwarded it was posted direct. I only collect my mail from my sister. What should I do? Thanks