I have been working my ass of to get my lands to go catholic, then when my king dies I see his son is orthodox wich gives me some problems. How can i get him to convert to catholicism?
Have your heir be tutored by a catholic. If he is too old (you need to start at age 6 to be 100% sure) just wait for next heir. If you don't have any catholics just invite catholic claimants to your court.
Usually if you Court Chaplain is catholic, there's a good chance of an event firing offering you conversion.