Being Scott’s twin and dating Isaac Lahey would involve:
Scott would not be happy with all the attention that Isaac is paying you. As much as he knows you’re your own person, he doesn’t trust Isaac all the much, especially with the amount of flirting he does.
But, you don’t mind at all.
In fact, most of the time you encourage it, because you think Isaac is cute and it’s fun to annoy your brother.
Sitting near you in every class possible. Isaac whispers to you through out most of the class which can get annoying but you let him off as soon as you see that adorable, cheeky smile.
Offering to tutor Isaac when he complains about how hard tests are. Although he doesn’t strictly speaking need a lot of help because he is quite bright, he likes spending more time with you- and there’s an added bonus of annoying Scott.
Getting distracted from studying when Isaac starts kissing you and flirting with you- this goes nowhere as Scott walks in.
Needless to say, after that you do most of the study session in Derek’s apartment where Isaac resides. Isaac assures you that it’s definitely not because of Scott, but you know it is.
Derek getting a little sick of the two of you being all lovey-dovey around his apartment.
Helping Isaac cope with werewolf transformations and such, and actually being quite good at calming him down during the full moon because you used to help Scott with his transformations when he was first turned into a werewolf.
Being part of the pack.
Gossiping with Lydia and Allison about Isaac and them finding your relationship with him adorable.
Isaac being partial to kissing you when you’re upset- usually it’s not on the lips, but on the temple, or forehead or cheek because it helps you to relax.
Falling asleep together after watching a movie, and Melissa seeing you two and thinking it’s adorable.
Scott? Not so much.
But, he does learn to accept the relationship after a while, even if he still is protective.
Toad's Cave 