How do you know they want them back in Poland?
Since you’re posting this here, I might as well give you my advice, coming from someone with a relationship with my dad where you don’t express feelings: have a talk with your boy face to face with nobody else around! Tell him you love him and it hurts you to not see him or the kids! Make it so he at least has to acknowledge that he hears you, he might surprise you with a reply, or not.
Come to him not from a position of power or disappointment, but love and understandment, and express your feelings towards the kids and how great they made you feel.
You’ll be happy to do this even if you tear up, but don’t post that here or you’ll be called gay!