As suggested by Shona, I am posting Ravan's family tree here.
Ravan's ancestors
Sage Pulastya was a mind-born son of Lord Brahma i.e. Lord Brahma created Pulastya from His mind.
Pulastya and his wife Havirbhu had to two very famous sons - Vishrava and Agastya. Both of them became great sages.
Ravan was born from Vishrava and his wife Kaikasi.
Ravan's children
Ravan had 7 sons:-
1. Indrajit
2. Prahast
3. Atikay
4. Akshya Kumar
5. Devantak
6. Narantak
7. Trishir
Ravan and all his sons died in the Ram-Ravan war.