Brina and Owen's fiancée are related.

"So, you were  saying that you know Owen's fiancée?" Louis asked Brins who just finished narrating whatever has happened today in his absence. 

W

"Yep. Just like I said, she is the underworld don's daughter" Brina told him. 

"But baby, how do you know her? I am not forcing you to tell. It's totally up to you" Louis told her, as he gently brushed his fingers through her hair. 

He kissed her forehead and lingered there for a few moments. "I will not force you if you don't want to talk about it" he gently whispered. 

After talking to Harry often, Louis started understanding many things about Brina. She might look like a genius, little vixen who is fearless and very calculative, however, when it comes to her past and her family, there could be nobody who is as insecure and traumatized as his girlfriend. 

Those things are like scars she could never get healed of.