Is it sexual assault?

A girl is around 8 or 9 is noticed by a mid-20s "family friend" and he says she's like a little sister to him. He gives gifts, sends letters and pictures, compliments her, and listens to her dreams.
Then when she's 14 he makes her believe she's going to kiss him on the cheek just like she kisses her dad and he tricks her into kissing him on the mouth. He then calls her while she's out of town and makes remarks like "you'd be warm if I was with you". 
Is this actually sexual assault or just a creeper? I'm almost 22 now and still have issues about this. Nobody in the family believed me because he was married to my cousin. They all think I  made it a bigger issue than it was. 
We are a close knit family and I ruined it all when I told my family I would no longer be around him. My mom and dad stood up for me but it alienated us from the entire (very large) family.
Someone recently told me this could be classified as sexual assault and I was completely shocked but I'm still not sure. 
I just need to know if this is really something bad or if I just need to grow up and move on.