Yes thats normal and does not have to do anything with OwnCloud itself but how you have configured apache.
In the default installation you would use Apache MPM (Multi-Processing Module) Prefork.
From the Apache Apache MPM prefork documentation:
A single control process is responsible for launching child processes which listen for connections and serve them when they arrive. Apache always tries to maintain several spare or idle server processes, which stand ready to serve incoming requests. In this way, clients do not need to wait for a new child processes to be forked before their requests can be served.
So as more client connection you have as more processes you will get.
You can configure the module in
# prefork MPM
# StartServers: number of server processes to start
# MinSpareServers: minimum number of server processes which are kept spare
# MaxSpareServers: maximum number of server processes which are kept spare
# MaxRequestWorkers: maximum number of server processes allowed to start
# MaxConnectionsPerChild: maximum number of requests a server process serves
You could also use Apache MPM Worker
Check http://www.garron.me for the differences:
Understanding Apache 2 MPM (worker vs prefork)