My ex is having another baby 🤢🤮

So it's a long back story but I recently just found out my sister is 20 weeks pregnant with my 4 year old son's father I have no idea what to think I left him for a bunch of good reasons but I can't believe this 🙄😣 I don't talk to him and haven't in almost 2 years and he hasn't been involved in my sons life since he was 6 months old I will also add I haven't spoke to my sister in the same amount of time as him because they were sleeping around with either before and after my son was born