Not to be confused with
Poopfeast420, a Yognau(gh)t.
Poopfeast420 (born December 2, 2011), more commonly known in the Yogscast community as "Sips' Son" is the son of Sips.
Similarly to his sibling, the name the Yogscast community know Sips' son as (Poopfeast420) is not the child's legal name, however his real name was unknown to the Yogscast Community until recently.
The name, Poopfeast420, comes from a Yognau(gh)t who consistently donated during the 2011 Christmas Livestreams. In honour of the donator, Sips "named" the child after the user.
Sips said in a GTA V episode that he plays a game called "No" with Poopfeast in which Sips constantly replies "No" to all the things Poopfeast says, and the child laughs incessantly.
As revealed in an episode of The YoGPoD, a name that Sips considered for his son was Dexter.
As of October 27, 2015, Poopfeast420 has a sister coined with the name Torbjorn.
 Poopfeast420 used to call Bowser in Super Mario 'Buster', inspiring the Super Mario Maker map name 'Buster's Basement' when he and Sips built maps and played the game together.
 During Triforce Podcast #51, Lewis revealed that Sips’ son’s name is “Kurt”.
Sips on Twitter ↑
Super Mario Maker - Dad Route