It's Not My Party
As much as Mac loves his little brother, I think there was a bit of a realization as all (or at least most) of the attention was on Lennon for the day of his party. For the first time, the party wasn't for Mac, and I'm sure he was a little hurt and a little confused.
If growing up comes from learning some "life lessons", then even though it was Lennon's birthday, Mac grew up a little that day as well.
It's Not My Party
As much as Mac loves his little brother, I think there was a bit of a realization as all (or at least most) of the attention was on Lennon for the day of his party. For the first time, the party wasn't for Mac, and I'm sure he was a little hurt and a little confused.
If growing up comes from learning some "life lessons", then even though it was Lennon's birthday, Mac grew up a little that day as well.