/target id ${Group.Member[1].ID}
and if you do want to target the pet, /target id ${Group.Member[1].Pet.ID}
Also, since inviting people to group they can end up in different orders, you need to be aware. If using EQBC i got around this by using this on my war when using my cleric to purely spam heals (no logic) and to target other group members by name where cleric name was my clerics name and TargetName was just the character i wanted him to target. No matter the order of players in group window it will target the player
/noparse /bct clericname //notify GroupWindow GW_Gauge${Group.Member[TargetName].Index} leftmouseup