Have you tried making a game out of it? Tried singing the ABC's and 123's?

I think that the biggest thing with kids that age is, if they aren't interested you can forget it. If your not making it "3rd old fun" then they are not going to want anything to do with it. They are still a little young too. I know that alot of kids learn their ABC's really early but some of them just don't. It doesn't mean that anything is wrong with them, they are just not ready yet. They will get it when they are ready and if you put on an educational show such as Sesame Street (I don't know if you have that or not) they will pick it up through that. They also have videos that all the kids like and they will learn alot from that. It will happen, don't rush them, they are individuals and will get it.