you as well as he are to blame for the accident
你和他都要对这次事故负责.
as well as
1.除…之外(也),同…一样(也),和,也,还
2.与…一样(程度)
3.既…又… [见well]
4.与…相同；不亚于…
5.此外,也
be to blame
该受责备(或指责)的；应负责任的；(是)某种不良后果的原因