Why won't my parakeets mate?

I have a blue male parakeet named Ikuto, and he is approximately 3 years old. (I've had him since I was 10, and I'm 13 now). Last summer, I decided to give him a lady friend, and I named her Skye. She is around 2 years old. From that day on, Ikuto set his eyes on her and tries to win her over, but she refuses to mate with him!!! He feeds her often, (it looks kinda like a kiss), but there are times where she will chase him away or run from him. I bought them a breeding house (Skye often likes to hide in there) and waited for Ikuto to make his move. Skye still refuses to mate with him. I personally don't know what is going on, but I get a feeling she's not into older male parakeets. :l What can I do to encourage them? Please help, and thank you!!!