As per your suggestions, I've added an A-Record like
xx.xxx.xx.xxx (www.site1.com) points to xx.xxx.xx.xxa (domain.com/site1) BUT what with my second, third, fourth, etc sites
Everything points to the location of domain.com. NOT site1, domain.com.
Use an A-Record and point http://www.site1.com to the IP for domain.com
I didn't say site1, I said domain.com and I meant it. They all point there.
Can't we have different IPs for child sites?
No. Everything runs on domain.com.