From what you describe, you may be looking for online remote soft / online remote firm dependency instead. (again with SG1 as child, SG2 as parent)
With this dependency SG2 will only run on system where SG1 is not running; if SG1 fails over onto the node SG2 is running on, SG2 will move to another system where SG1 is not online.
In both cases, SG1 must be up before SG2 can come online. The difference between the two is whether SG2 remains online (on any node) if SG1 faults and cannot come up/failover to any other nodes.
http://sfdoccentral.symantec.com/sf/5.0MP3/solaris/html/vcs_users/ch_vcs_group_dependencies6.html
with online remote soft:
- if SG1 faults and cannot come up/failover to any other nodes, SG2 will remain running
with online remote firm:
- if SG1 faults and cannot come up/failover to any other nodes, SG2 will be taken offline
Note: for purposes of switching you may still need to offline SG2 before switching SG1 as an intentional/manually triggered switch is different to a failover due to fault (which is where the sg dependency comes in).
Hope that helps.