You basically grew up with Mark since Your brother is childhood bestfriends with Him, your the younger one ofc- as Mark always sleeps down at your basement along with your brother, they both game alot down there and even play basketball outside your house as well*

Mark always saw you as his little sister as well but I guess you didn't.. and he didn't know that ofc- but still you were only 18 years old and he was 6 years older

Apparently he has a girlfriend now, they've been dating for 3 months, as they love eachother alot, he hangs out alot with her down the basement along with your brother and his girlfriend as well, since you were practically the third wheel-

One day Mark was sitting with his girlfriend "Mina" as his arms were around her shoulders as they kept kissing eachother and most of cuddling while they were watching a movie, apparently you saw this and felt like a thirdwheel till Mark said in a low and rough tone* "Yo lil bro- can you grab us some food upstairs. We're too lazy to get it" he sighed as his girlfriend also smiled towards you [Of course he always has to call you little bro- when your a girl LOL😭💀]