Brother & Sister tattoo opinions?

Hannah • Girlfriend of a U.S. Marine Veteran

So my very best guy friend (who is also one of my boyfriends best friends) is like an older brother to me. Always making sure I'm having a good time but he's the first one there if something happens to me or the first one holding my hair back if I'm a little too drunk haha

Basically he's my brother from another mother lol

We wanted to get some tattoos that showed our relationship. He said that he wants them close our hearts because it will be more meaningful and I agreed. So he is going to get it over his heart (on his pec) and I will get one under my boob/high upper ribs area (more towards the side)

His is going to say "My sister's keeper" and mine will say "My brother's keeper" but we also wanted incorporate some kind of picture/symbol. We were thinking maybe he has a lock and I have a key with it?

Was wondering if anyone had any other good ideas or suggestions? Should I place it somewhere else?

I do have this rib tattoo already so I kinda need it small in order to fit