Well not exactly an ex but the girl next door who he had a massive crush on growing up.
She is 5 years older so wasn't interested romantically but their families were good friends and so they spent holidays together and they loved each other like family.
She moved to another country following university and they stated in touch via Facebook and social media.
She's now back in the U.K. and they (she and ny boyfriend) have been hanging out.
She texted him whilst my boyfriend was showing me something on his phone. The message said "missing you babe. Let me know when you're around for a chat xxx"
He immediately shut his phone down and I asked him what was going on. He said that they'd been reminiscing over old times and he confessed that he'd fancied her when he was 13. She told him that spending time together recently was the best thing and that she'd fallen in love with him. Then she kissed him 
I asked him what happened next and he swore nothing happened and that whilst he loved her as a friend, it was me he fancied and wanted to be with.
I'm really confused. She knows about me so what was she doing?
Boyfriend swears nothing will ever happen between them. And that he isn't encouraging anything other than friendship that has spanned over 20 years.
Should I be worried?