Complex sentence: The festivals in Sikhism are mostly centred around the lives of the Gurus and Sikh martyrs, the most sacred events being Vaisakhi and the births of Guru Nanak, Guru Ram Das and Guru Gobind Singh.
Split into simpler sentences: The festivals in Sikhism are the events that are mostly centred around the lives of the Gurus and Sikh martyrs. The most sacred being Vaisakhi and the birth of Guru Nanak Dev, Guru Ramdas and Guru Gobind Singh.