by the way, let me say this is one of the wonderful things about My geese, Pilgrims, they are auto sexing , at birth, , but not only at birth, ,, their whole life long, ( sorry I know that doesn’t help you with these)
looking again i think they’re ganders because the necks are so long . so basically i’m guessing. iwould test their behavior to try and find out. like walk towards them and see if they both come at you with outstretched necks …
it's generally recommended to keep new birds separate for at least a week (or two) "quarantine" to watch them for health issues. Put them where they can see your goose through a fence so they all get used to seeing each other.