Fiancé cusses at me

I’m starting to get fed up. I have a 5 year old and a one year old and when my fiancé is mean to my eldest who he’s not his dad I of course stand up for him. Well instead of being calm my fiancé throws the “f bomb” screaming at me.

I’m starting to get pissed off! I don’t want my kids thinking thats ok

He tells me shut the fuck up in front of my kids . Like is this normal???