Sen'tran conceives this child with Jo right before he dies and commits Lenn to marry Jo and raise the child. He does this partly to give Lenn and Jo a place in the community after his death, knowing that his genetic offspring will be highly valued by the community.
Sen'tran named the child Sen'tran Landon, but Harris refuses to call the baby Sen'tran so he sort of gets renamed Landon Jenzar.
Landon grows up with Anton as a sort of older brother, and they are very close. When Anton leaves to start the teraforming of Paragangia Landon eventually follows him, although I don't know the time frame on any of those things. Landon loves the Dragon Ferrets which Anton is keeping as pets on the Marrion Jay.