Guy friend is ruining my relationship (lengthy post)

Background information: 
i've been with my boyfriend for a little over a year now. We are both approaching this relationship with caution due to both of us being hurt from our past relationship. We have a special thing going. We have a healthy balance between passion and personal space. We try not to think of the future too much (we feel it adds wanted pressure to our new relationship). We are simple people for the lost part. If there's an issue we talk about it and solve it. Neither one of us likes it when people dwell on something for so long without bringing it up. 
The problem:
There is a family friend. We've known each other for over 14 years but we have been close for the past 8 years. I can't see myself as anything more than a friend to him (yes he is friend zoned). He did tell me that he was into me and I remember that I was into him when I was younger but I grew out of it. I kind of backed off for a while. Recently my boyfriend expressed his concern about this friend. I explained to my SO that he was just a friend in my eyes and its hard to just cut someone out of your life especially when he understands things that others can't (I couldn't figure out a way to phrase it). My boyfriend read some messages between the friend and I. and I admit they do seem flirty. Which is why I wanted to tell my SO about it but he got to the messages first. I feel like I spend a lot of my time with him watching what I say and trying to make it up to him. It posses me off because it's not like I slept or even kissed the friend. 
The question: 
how do I deal with the friend? Should I ignore him and block him from all communications? AND what should I tell my boyfriend to make him more secure (let's face it I know he's jelly and insecure about the situation)? I just don't know how to show him or convince him that I'm not interested in the friend.