I'm going to call my girlfriends brother a chubbier version of her other brother
Why are you going to call him chubby?
He looks like a chubby version of her other brother.
Calling someone chubby might hurt his feelings. It would be best to not refer to his weight.
Lol, it's okay. I'm pretty sure he gets called that all the time, plus my girlfriend isn't fat.
It's wrong to make fun of someone for their weight. This is hurtful and can cause him to feel down about himself. Instead you should avoid saying anything if you think it will be mean.