Kusha and his Chief Queen Kumudvati
During the reign of Shri Ram, Kusha and Lava had married daughters of Maharaja Bhurikirti named Champika and Sumati respectively in a Swayamvara.
Kusha had nine daughters with Champika and Lava also got children from Sumati. Lava ruled North Kosala and Kusha ruled South Kosala. His capital was Kushavati.
Rishi Agastya had told Shri Ram that Kusha and Champika won't have any sons and Kusha will have a second wife named Kumudvati who will give him many sons. Eventually Kumudvati gave eight sons to Kusha and eldest son was Atithi who succeeded him. Their daughter and also his youngest daughter was named Champakmalini.
When Shri Ram went to his divine abode to reunite with Mata Sita, Kusha came back to Ayodhya on the request of its deity. He was offered hand of Kumudvati in marriage by her brother Naga King Kumud along with Kusha’s lost golden bracelet in Sarayu river. He married her immediately and made her his Chief Queen. Their son Atithi became their successor when Kusha died and Kumudvati not able to bear sorrow of separation from her husband went behind him in heaven.
The reason they are not as popular as Shri Ram is because their life wasn't as sorrowful as Shri Ram and their deeds were not Divine. Yes, they fought demons, did charities and were great Kings but they could never have the divinity of Shri Ram.
The deeds of Shri Ram were not less than divine, he is called Avatar of Vishnu in Valmiki Ramayana and he bore so many sorrows, grief and pain and yet he never lost himself and bore everything with patience. His life teaches us moral values, strength, patience, respect for women and many other things.
The best book to understand the personality and character of Shri Ram is Ramcharitmanas by Goswami Tulsidas.