No. There's no reason a non-family individual twice the age of a child should be hanging out with the child socially. What good could possibly come of it? The first problem is that an 8yo has the ability to give out his/her contact information to anyone.
In this scenario you have, for all intents, an adult in a relationship with a very, very minor child. This is suspicious in and of itself as there couldn't be any real shared interests. It's creepy.
This is dangerous in every sense.