coexist

hi gurus

I have the follow env. server 2008 cluster and sql 2008 enterprise, I have multiple sql 2008 instances and all of them enterprice sp2 but I need to create a new instance on the  sql cluster, so the question is

2 instances  sql 2008 sp2    1 instance 2008 R2 std 

2 Instances sql 2008 sp2     1 Instance 2008 enterprise r2

can they coexist like that?

thanks gurus