I heard many stories about different gods in Hinduism. A God's life also rolls in many stages as a human being like birth, love and marriage. I have a doubt that most of the God's followers didn't bother to have tales on the life of God after marriage. What is the reason behind that? Or are there any stories which are hidden from the outside world?
Your assumption is not correct. There are many stories of Devas after marriage.
Stories of Lord Shiva after marriage are quite famous. Stories of Ganesha and Kartikeya are quite famous across India. Even Stories of Shiva being born as hanuman, Shiva granting Pasupatastra to Arjuna and many such stories are famous which happened after Shiva's marriage with Parvati. People usually worship Shiva's family as whole.
Indeed, main story of Ramayana starts only after marriage of Lord Rama and Goddess Sita. Ravana kidnapping Sita and Rama killing Ravana happened only after their marriage. Stories of Sita's exile and Lava-Kusa are famous too.
This list is innumerable.