Phone passwords

What do you think of this?...

My bf knows my passcode & I have his thumb print for my phone but I don’t know any of his. I don’t care but I’m not sure if I should still allow this when he doesn’t even try or tell me his..

Thoughts?

Edit- I’m not asking to put my finger print on HIS phone I’m saying he’s doing it for MINE. So he knows and has access to anything on mine. He added his thumb to my phone, I don’t care to go through his but not sure if this is fair?