Guru Nanak Dev Ji was married to Mata Sulakhni Ji. His marriage to her took place in the town of Batala. The marriage party had come from the town of Sultanpur Lodhi. He had two sons from this marriage; Sri Chand and Lakhmi Chand. Sri Chand founded a renunciate/ascetic sect known today as Udasis when Nanak did not choose him as his successor. The younger son grew up to become immersed in worldly life.
Guru Nanak Ji's teachings come down today foremostly in the Guru Granth, a vast collection of revelatory verses recorded in Gurmukhi.
From these some common principles seem discernible. Firstly a supreme Godhead who although incomprehensible manifests in a variety of religious forms, the Singular 'Doer' and formless source of all forms. It is described as the indestructible or timeless form and in both impersonal and personal forms. Salvation or liberation depends on the grace ('nadir'- glance) of God alone and although outside the power of the individual, manifests through the individual whom is seen to be unceasing in their efforts. Religious awakening is compared to undergoing a living death.
Guru Nanak Ji describes the dangers of the self (haumai- 'I am') and calls upon devotees to engage in worship through God's name and singing of God's qualities, discarding doubt in the process. However such worship must be selfless (seva)- which could be said to be similar in principle to the nishkaam worship elaborated in the Bhagavad Gita. God's name cleanses the individual to make such worship possible.