You need to register to become a member too in order to get your Sam's club membership card. This is because the fact that your spouse is a member does not prevent you from becoming a member too. You can apply online from their website. Visit http://www.samsclub.com/sams/homepage.jsp.
U should be able to get a second card because u are spouses or it may be like cell phones and primary card holder and secondary and so on and i think it is cheaper for secondary members to be added to their account