Sure! That’s totally up to you and your church leadership. We’ve seen some churches hold one spot in each group open to invite people from outside their church, as a way to introduce the program to other churches. We’ve also seen churches partner together to create mentoring programs. This works especially well in smaller towns or smaller churches that can struggle to put together a full group(s) on their own every year.
To us, the most important thing is to make sure everyone is on the same page about what is involved in the group and where you’re headed! Although one caution, it’s probably not best to invite someone who is exploring faith and maybe checking out your church. They need community too, but in a group like this, they will become the “project” and distract from the growth of the group as a whole.