Kkkkyyyyyaaaaaaaaaw is do cute
But kinda wrong cause their step bros

this was very nice, I would,however, recommend you slip the step-brother information into one f the first sentences. Let's see...how about:
""Sebastian! Sebastian!" My step-brother waved his arms the moment he saw me." or if you wanted to keep it a surprise put it here:
"Wah! Wh-what are you doing?" I lifted him in a hug…

"Sebas-mph?" And finally kissed my step-brother where I really wanted to kiss him the most: on the lips.

Remember when real authors write books they don't need tags like "By the way..." They utthe information in the rags or in the exposition.
Good story. Well done.

love "brother"/" brother" ciel sebastian love!

Neat story!