Venting a basement half bath

I have a half bath in the basement that I had roughed in when the house was built two years go. I am bit confused on how to vent this properly. The bathroom was roughed in....in a corner of the basement directly under the laundry room. From left to right I have the following: A pipe for the toilet with a vent directly behind near the concrete wall (which I framed to fit in my stud wall). To the right of the toilet drain a bit closer to the wall is a drain pipe for the sink. To the right of this (tucked in corner and also in my framed wall) is the drain for the upstairs laundry which also connect with the sink and then the toilet under the slab before exiting the house. On the ceiling above the vent for the toilet there is a capped vent that eventually exits the house threw the roof. This vent is separate from the other vents for two bathroom upstairs on the other side of the house. My question is how to vent both the sink and toilet. My father in law seems to think all I need to do is take the toilet vent up the wall to the vent in the ceiling. That makes sense, but what about the sink? Do I need to run a vent line from the sink to the "toilet vent".. or since it is all connected under the slab would that vent serve both the toilet and sink?