error when creating post

Here is the Error I get when I try to create a new family, member or etc.

Warning: fopen(/home/proposit/public_html/test/wp-content/plugins/family-tree//family_data/family_11.json) [function.fopen]: failed to open stream: No such file or directory in /home/proposit/public_html/test/wp-content/plugins/family-tree/includes/custom-meta-box.php on line 466
Cannot open file (/home/proposit/public_html/test/wp-content/plugins/family-tree//family_data/family_11.json)

https://www.ads-software.com/plugins/family-tree/

Please advise a solution