Arlan usually isn't fond of when people call him 'big brother'. It's different when it's you though. Knowing that it's because you're a regressor so you're probably just doing it out of innocence.

"Big brother is here, silly, did you need something?" Arlan asks fondly, ruffling your hair gently.

Today at Herta's Space Station it's actually pretty tame. So it's perfect for Arlan to take care of you and maybe coddle you the tiniest bit.