Sai Satcharitra mentions his past life as 'Zindafil Ahmed Jam' , who blessed Humayun to have a son in future and get back his lost Mughal throne.
At the same time, Mukund Brahmachari, who was doing severe penance to eliminate muslim rulers from India, due to his hatred for muslims, had to take birth as Akbar (Humayun's son) and balance that hatred karma by living as muslim, but respecting and following hindu traditions (even marrying a hindu princess Jodha).
Guru Charitra (Narasimha Saraswati) and Akkalkol Maharaj biographies too have such instances where brahmins were born as harijans due to their ego and hatred towards other castes. [This teaches a lesson for religious intolerant people]
Sri Pada Vallabha gave boon to a mother of dumb guy that he would be born as her son in next life.
That happened when he reincarnated as Narasimha saraswati to his mother Amba-Bhavani.
His other boon was to a Rajaka (washerman), who was born as Allauddin-II of the Bidar kingdom, who met Narasimha Saraswati in his old age.
Also Sri Pada Vallabha Charitra mentions that Mehboob Subhani was reborn as Waris Ali Shah (1819-1905), who was guru of Shirdi Sai Baba.
Infact, Sai Baba was partial amsa of Hanuman.
During that period, Vatsavai Narasimha Varma, a landlord near Pithapuram in Andhra Pradesh, was a follower of Sripada Vallabha.
He was blessed to be reborn as Chatrapati Sivaji.
Sripada's elder brother Sridhar Raja Sarma, was reborn as Samartha Ramdas, who was Sivaji's guru.
Madhavacharya, who met Sripada Vallabha was born as Vidyaranya Swami who guided Harihara and BukkaRaya to establish Vijayanagara empire of Hampi.
In next life, he was govinda dikshitulu (born to vidyaranya's brother sayanacharya [who calculated speed of light, distance between sun-earth etc] and becomes Tanjavur minister.
There are many such incidents in past.
In present, ex-resident APJ Abdul Kalam is believed to be reincarnation of Tipu Sultan and his guru Homi Baba to be tipu's father Hyder Ali.
Tipu lost the kingdom earned by his father, due to lack of training in Cannons and Gunpowder usage.
Due to that frustration, both father-son due were reborn as scientists who worked for atomic research and ISRO to develop India's own science.