Combining objects based on another layer

I'm trying to combine a building layer and a parcel layer. The goal is to combine all the buildings on one parcel to one object. The only relationship the buildings and the parcel have is spatial. When I use spatial join the parcel gets combined with one building, and this for all of the buildings on the parcel separately.So the question is, how can I combine the different buildings on the same parcel? Already thanks for the help!