Landlord asked for second security deposit from roommate

I moved into a 2 bedroom apartment in New Jersey and I put my name on the lease, signed everything and told the realtor I would either move in with my brother or a close friend but I will move in with someone. The landlord found out I had a roommate and asked for a second security deposit half of what I initially paid. I’m unsure of if this is a legal practice or not. Thank you.