u/Beautiful_Talk109

I read this in the 2000s at school, but I'm not sure when the book came out. There was a brother & sister whose parents passed away or went missing. Their evil family member (unsure if it was aunt, uncle, etc) tries to take the family's big mansion but the kids take them to court to get ownership of the house. I think the house may have been inherited, & not the house the kids grew up in.

I distinctly remember the cover. It was cartoony, & had a mansion with the brother & sister in front of it. The sister was wearing a judge's robe & holding a gavel.