Is it normal That My Step dad does this??

Thanks for the support!! Here is where the story gets crazy. It's not so much me who is being hurt by this. You see my younger sister who was pregnant when my mom passed away went into labor and gave birth to her daughter 11 hours after my mom died on the SAME day!! Awesome hey? Anyway she still lives in my mom and dads house and she is devastated by this cuz he is spending no time with her and his granddaughter. He works up north 3 weeks on and 10 days off and when he's home he is drinking and hanging out with this woman that's why I am mad!!!