When Kim comes to stay with Lurgan in Simla for the first time, he finds an orphaned Hindu boy living with Lurgan as his son. Lurgan has taught this kid the Jewel Game, and seems to have high hopes for the boy's powers of observation. The Hindu boy is hugely attached to Lurgan, and calls him "my father and my mother" (9.83), all wrapped up in one person.
However, the Hindu boy is not the world's most stable individual: when he sees Lurgan paying attention to Kim, he actually tries to poison both Lurgan and Kim out of jealousy. We talk about the somewhat weird relationship between Lurgan and the Hindu boy in Lurgan's "Character Analysis." Here, we'll just say that Kipling puts an end to this bond by mentioning, in a quick throwaway line, that the Hindu boy has gone away to be married and has left Lurgan's household (10.6) by the time Kim returns to Simla a second time.
Clearly Kipling recognizes that the relationship between these two characters is too intense to be sustainable, and sends the Hindu boy offstage before he can cause any more trouble for Lurgan.