If you keep watching, some answers are explained.
It's getting good...
If you watched last episode, you'll see why Oliver cares for Tommy so much.
Tommy was a really good guy.
And it's nice that he can finally talk to his sister about his secrets...
And his sister... dang she keep pressing him all the time for his secrets...
Why can't she get it through her thick head that he only never tells her things to protect her.
She's slowly starting to understand and see that now.