Sain wedi'i Rhannu

AITAH for telling my dad's pregnant girlfriend that he already has three kids I have nothing to do with and her baby will be no different? I (17M) grew up with my mom. I only ever saw my dad one day a month and that has not changed after all this time. My mom and I tried to end that visitation but the judge said since dad never skipped a day it made sense to continue until my 18th birthday, which is in October. My dad has dated a few women over the years and he has three other kids out there. M