Confusion Facebook and iPhone! – Ask different

I have an iPhone 6SPlus on which is my original Facebook account. I've stopped using Facebook for a while, I basically had no time to do it, so I changed Facebook's name to my husband's name because he wanted to keep in touch with our friends, etc. to open his own FB account, it seemed like the easiest thing to do! A few years later, I decided to open a new Facebook account and add it as a second user of my iPhone, which is not a problem except when I want to share something from Safari. This shows that the phone is connected to my original Facebook account which, although it is in my husband's name, was originally configured to my name! Is it possible to change these details in the iPhone?