- "Hey, Kate, wanna watch me play football?"
- ―Mark to Kate
Mark Sanders (born July 3, 2005; current age: 8) is a supporting character in Sibling Rivalries, and a minor recurring character in Sibling Rivalries: The Next Chapter. He was the boyfriend of Kate McReary, but they broke up off-"screen", and Kate later starts "dating" Salvador Real.
Mark returns in Season 3 with a slightly larger role. Mark finds out that Kate is now dating Salvador, and admits that he still loves her, so he tries to get her back. At first Kate isn't happy to see Mark, but after finding out that Mark never broke up with her, they get back together, and Kate breaks up with Salvador.
Mark will reappear in The Next Chapter, where he and Kate are still a couple.
- Sibling Rivalries Pre-Series
- Sibling Rivalries Main Series (Season 1)
- The McRearys Get Schooled! (mentioned only)
- Locker 239 (first appearance)
- San Salvador's Story (mentioned only)
- Sibling Rivalries Main Series (Season 2)
- The McRearys' Halloween Special! (appears as a Halloween decoration)
- Happy New Year! (mentioned only)
- Sibling Rivalries Main Series (Season 3)
- Sibling Rivalries Main Series (Season 4)
- Sibling Rivalries Main Series (Season 5)
- Trading Places (non-speaking cameo)
- A Christmas Story (mentioned and pictured only)
- Straight Outta Green Bay (mentioned and pictured only)
- Uncle Cameron Moves In (mentioned only)
- The Lockdown (non-speaking cameo)
- ApRiL fOoLs DaY: wIsCoNsIn StYlE!
Total Number of Series Appearances: 8/45
- Sibling Rivalries The Next Chapter (Season 1)
Mark has no appearances in Season 1.
- Sibling Rivalries The Next Chapter (Season 2)
- In Loving Memory of Aiden McReary (mentioned only)
- So far, "Locker 239" was the only physical appearence of Mark, until Season 3.
- Mark is always seen sweaty from playing football, except for his appearances after The Pool Date.
- It is unknown if Mark is on a football team, such as the Wisconsin Warriors.
- Retcon: Mark and Kate break up in "San Salvador's Story", but it is not seen. However, at the end, Kate is still seen happy and does not mention breaking up with Mark (although it may be because she accidentally mistaked fruit punch for liquor, like the other siblings did). Breaking up with Mark is not mentioned until "Happy New Year!", but in The McRearys' Halloween Special! (which takes place between "San Salvador's Story" and "Happy New Year!"), she is still seen to like Mark, although they broke up. Of course, "Happy New Year!" was written at least a month or two after the Halloween comic.
- Kate breaking up with Salvador and getting back with Mark in Season 4 was a choice by GTA Nerd, as he felt that these two were a better couple than Kate and Salvador, as they are the same age (unlike Kate and Salvador, who are eight years apart).