terrible person, i am

Scenario 1:

This happened sometime back; more than a year ago.

Was playing Kinect with a group of friends at a friend's place when I spotted a woman coming down the stairs. I automatically chirped "Hello Auntie!" in a friendly gesture for having assumed that was his mum. Apart from turning silent, everyone else also turned their gaze to me.
My exuberance quickly turned to awkwardness and embarrassment when I realized my folly.

It was his elder sister. And she's really just 2-3 years older than we are.

I was so embarrassed for insinuating she looked much older than that (it was the dim lights I swear) that I wish I could dig a hole in the ground, jump into it and bury myself.

Apologized profusely afterwards but it probably didn't help to change her terrible impression of me.

Scenario 2:

This happened last Sunday.
Spotted an unfamiliar and rather mature(-looking) lady sitting at the usual gang's bench at ECP; since she kept to herself her iPad most of the time, and no one's actually done any introduction, I did not have any chance to talk to her.
Only realized that she's somehow related to a friend (let's call her X) when I saw them chatting much later on the grass some few steps away from the stone bench.

When X came back to the stone bench (her friend's still sitting on the grass),
out of curiosity and to confirm my guess, I asked her without hesitation, "X, your mum ah?"

To which she smacked me hard on my arms and bum,

"NO IT'S MY FRIEND, AND SHE'S THE SAME AGE AS I AM (i.e. 29)"

Couldn't help but started howling with laughter and gasping in mock-horror.

The people around who caught the conversation started laughing too; though I wasn't too sure if they were laughing at my gungho-ness in asking such questions (without consideration of people's appearance) or the fact that X's friend really resemble a motherly figure.

I'm truly a terrible person. Karma will come my way soon, I'm quite sure of that.