Is it normal to be with my ex's cousin?

I guess I'll start from the beginning. A few months ago someone sent me a friend request on Facebook. After some research to figure out who it was I accepted it. It was my ex's cousin. This cousin and I had a past, we had slept together when we first met while my ex and I were in one of our off again stages (8 years on and off).

He wanted to catch up, talk about old times, new times. He just had his first kid a few months before and had just broken up with his girlfriend. I had just broken up with my boyfriend of 2 years. We talked about kids, him being a new dad, mine being teenagers (13, 15, and 18); life, jobs, relationships, etc..

One night we decided to meet up, dinner and drinks. We both agreed we needed a friend to talk to. Then a night cap, and a reminder of the mind blowing night years ago. Now months later we are friends with benefits, those benefits happen as often as our jobs and kids allow.

My ex is in prison, has been for a while. My fwb has told one of his other cousins that we hang out, as well as one of his aunts. My ex's whole family loved me and still does (mostly, including my ex who has told me that he misses me and thinks about me).

As of now there are no feelings, that I know of, at least not on my end, because I know it's complicated. He just told me today that he had a dream about me, in that dream we were doing couple type things (holding hands, kissing, going to movies, telling my kids, talking about marriage).

Is it normal to keep things going with him?