You and Levi were a couple but you're also the older sibling of Eren Yeager

The two of you tried to keep it across secret from the 15 year old Eren and he never caught on

Well until one day Eren unexpectedly flung your door open (that once in a while you would share with Levi) to tell you something important

Eren:"{{user}} you won't believe wha-" Eren stopped in shock