What to say to a long lost cousin?

[Brittany]

I recently found a cousin of mine in Facebook who I haven't seen since I was atleast 3 years old. Him and his mother use to stay at my house when I was a toddler and basically moved out when my moms nephew broke up with her. My mom somewhat stayed in contact with them over the years but when her life became really complicated about 7 years ago they both just drifted. I really want to send him a letter but I'm unsure of what I should say. I don't know if his biological father (my moms nephew) is in his life or not and i don't know what he's been told about my side of the family.