AITA for holding in my laughter because my brother was crying after finding out his ex is getting married?

I (16M) was chilling with my mom in her room when suddenly our front door was unlocked and opened. My brother (21) comes in. He never really comes to our house anymore, but when I saw a closer look at his face, I saw some tears and he just started crying in front of my mom. I immediately had to excuse myself out of the room because I didn’t want to be apart of this. After a bit of eaves dropping, my brother finally says something after standing there for like 2 minutes and utters the words "She’s getting married." I immediately knew what had happened and I had to hold in my laughter.

For some context my brother was pretty much a dickhead towards me growing up so watching him cry really fuelled my ego, I mean I can make the argument that my brother laughed at me when I used to cry.

After sometime of him crying, my mother messages me on Whatsapp to go get a glass of water. It took a long time for me to do that as I was trying to compose myself and not just bust out laughing.. Entering the room, I just see my brother crying on my moms lap and that’s when all of that pressure in my chest from trying not to laugh comes back and I had to lock in HARD. My mom saw me holding in my laughter from covering my mouth with a grin.

She later messaged me again reading
"Thats not nice." Which I left it on seen because I thought it was lowkey stupid. Few minutes goes by and she calls me to go grab some tissues. So I did what she said.. I gave her this huge tall thick roll of tissue paper lol.

After that, few minutes goes by before him leaving the house, which I probably think its not a good idea for him to do as his vision is filled with tears and the roads are all icey. Coming to my moms room, she goes on at me about why I was laughing at him, which clearly I wasn’t.. I was only holding it in.

I replied with "He would laugh at me too if I cried" and her response was "That’s different though" and she asked "Do you feel any shame?" which i respond with "No." before telling me to leave her room.

I think im the asshole but I don’t think im wrong, give me your opinions