A two-month-old infant choked on milk after his mother left him under the care of his eight-year old sibling.
The mother said the boy was being fed by the sister when he choked.
Ms Janet Gathoni said she rushed the baby to a nearby clinic but he died while on the way.
The incident, which is being investigated by police happened at Mathare North Area 3, Nairobi.
It was reported at Muthaiga police station 30 minutes after midnight on Thursday.
Separately, a man was lynched in the city’s Dandora Estate.
A watchman at Supereagle court within the estate told police that he noticed a three-man gang that was mugging pedestrians.
He raised an alarm and a crowd that responded cornered one of the men and stoned him to death.