Some people are very sensitive about their age. I remember I tried to plan an out-of-state party for my father-in-law's birthday and he said, "No way!" and the reason he gave was he didn't want his lady friends to know how old he was (he was going to be 80 and his lady friends were in their 50's). He use to have his grandsons when they visited call him "uncle".

I myself would not be thinking of the lying but more curious about what he thought 2 years was going to do for him? I think the attempt to "hide" something from himself is worse than the lie in this instance. Is the difference in your all's age very great? If you are a lot younger, I'd say he has a pride issue or is afraid you will be horrified or something about his actual age. Sounds like insecurity on his part, not deceit. I would almost rather have the deceit as that would be straight-forward; insecurity/self-esteem issues can be harder to deal with since they are 100% from him with no "reason" outside, nothing tangible to gain like lying has. You can't make another person like you (except maybe a very shallow one that cares about age like the liar does).