"I saw the man which is with the girl" is not grammatical.Originally Posted by basurero
Firstly, I don't think you can use 'which' with people.
"I saw the man who is the with girl"
In which case in Russian it would be:
Я увидел человека, который с девочкой
or
Я увидел человека, с котором девочка
Maybe both are OK.