supposing i own domain aaa.com and bbb.com and i have the IPs 1.1.1.1, 1.1.1.2, 1.1.1.3 and 1.1.1.4 on my server

i got to make:
ns1.aaa.com -> 1.1.1.1
ns2.aaa.com -> 1.1.1.2

now how to make:
ns1.bbb.com -> 1.1.1.3
ns2.bbb.com -> 1.1.1.4
?

just need to add it on /etc/hosts?
even it having the same "subdomain" (ns1 and ns2) as the other domains?

thanks