"They love themselves, and we love ourselves."
Translation:Ili amas sin, kaj ni amas nin.
Si(n) is the reflexive pronoun, while mem is a short little word sometimes used to apply pressure to the importance of it being himself/themself/herself etc.
Myself = mi (mem)
Yourself = vi (mem)
Himself = si (mem)
Herself = si (mem)
Ourself = ni (mem)
Themselves = ili (mem)
He loves him(self) = Li amas sin (mem) [here mem might be added for extra clarity that it is himself)
Li amas lin = He loves him (someone else)
Don't focus on the word mem in the beginning as it's just there to emphasize.
Focus on learning the word si(n).
In a conversation there are only one speaker, and one listener, who might be , or refer to the participants in the conversation as, a group. So it is obviously that us refer we and vv.
But there are several persons/groups than do not participate in the conversation, and to tell that that subject is the same as the object, you use si.
Everything you wanted to know about mem and si.
Some things you didn't want to know.