Boyfriend's dad!!

Me and my boyfriend have been together for a year and he has met most of my family even though they live in the Netherlands and stuff, he is like the most serious boyfriend I have had and he's the only one to have met my dad who live in the Netherlands as well. However, I don't know if he feels the same because I've never met his dad and it really bothers me as he lives round the corner from where my boyfriend lives along with his sister and her boyfriend which I have never met either... I don't know how to tell him that this bothers me because he would just act really funny around it... Help?!