His family want him to marry a girl who is not religious and they say that she will change in time

The Prophet (peace and blessings of Allaah be upon him)
commanded the one who wants to get married to look for a religious woman. He
(peace and blessings of Allaah be upon him) said:  “A woman may be
married for four things: her wealth, her lineage, her beauty or her
religious commitment. Look for the one who is religious, may your hands be
rubbed with dust (i.e., may you prosper).” 

A wife is a life-long companion, and she will take care of
his household and all his affairs. She will be the one to bring up and teach
his children. Religious commitment is the thing that makes a woman chaste
and keeps her away from bad things. So you must choose a wife from among
those women who are religiously-committed and fear Allaah. 

What I think you should do is to strive to influence her and
make da’wah to her through your family or some of your mahrams so that she
will improve and adhere to the straight path. If she adheres to the straight
path and improves, then marry her. 

Otherwise, I think that you should look for someone else, for
you have no guarantee that you will be able to influence her; she may not
respond, or you may be influenced by her, for no matter how much faith and
taqwa (piety) a person may have, he is still human and is still subject to
change or influence.