The Orange Democratic Movement (ODM) party has said the Kibra constituency seat has never at any point remained vacant, despite the absence of area MP Ken Okoth.
Okoth was away in France where he received cancer treatment for five months, with the party now saying that his office was being held by Westlands MP Tim Wanyonyi.
In a tweet on Monday, ODM revealed that Wanyonyi has been doubling as the Kibra MP while Okoth was away.
Congratulating Tim, the party termed his decision to stand in for his colleague as the true spirit of brotherhood.
Okoth returned to the country last weekend, and made his first appearance on Sunday during the Kibra Music Festival.
"Westlands MP Hon Tim Wanyonyi has been representing Kibra MP Ken Okoth in the Constituency for the period he was away for treatment. Yesterday he joined Ken for the annual Kibra Music Festival. This is the true spirit of brotherhood," the party wrote on Monday.
Both MPs are in office on the ODM ticket, with Wanyonyi having already announced gubernatorial ambitions for the Nairobi county in the 2022 polls.