Does anyone know this book or has read it before?

Has anyone ever read a book about a boy and a little brother who go somewhere, meet this guy along the way with a magical house, and go somewhere.. Okay, so this is what I remember from the (near the end).
A boy and his brother go with this guy (a guy they met who saved them before they were going to get killed because these kids stole a bird from a shop and gave the bird to the boy and his brother and the shop owner thought is was the boy and his brother and was going to kill them for lying since they kept saying they didn't do it), go with this guy to a doctor or some place and as soon as they were going to leave the "place" they heard a whistling and recognized the whistling. They turned around and saw the person who was whistling the song. They realized it was their father and they ran to him, hugged him, and began crying since they haven't seen him in a very long time.
The cover of the book is in the ocean with a lighthouse..

That's all I remember. HOPEFULLY someone does know the book because I LOOOVED the book very much and would like to buy it since I read it in a library years ago.