I heard Damu Anna was childless. How did Sai Baba intervene in his personal life regarding this issue?

Yes, that's correct. Chapter 25 mentions that Damu Anna, a wealthy and devout follower from Ahmednagar, had two wives but was without children. This personal struggle is presented as a backdrop to his story of faith. The text explicitly states that 'By receiving Sai's blessings, he was blessed with sons.' This event is cited as an example of Sai Baba's nature as an 'Ocean of Mercy' who wards off the misfortunes of his faithful devotees and grants their desired objects. This blessing illustrates how Sai's grace directly addressed a significant source of suffering in Damu Anna's personal life, reinforcing the theme of one-pointed devotion leading to the fulfillment of desires.