Step parenting troubles

Is there anyone who can help me navigate this whole step parenting thing. My husband has two kids that come and visit on the weekends.

Let me say, they're fun kids and fun to be around and this is in no way a post to bash these awesome kids.

That said, often times my husband is afraid to discipline them or correct them because he feels like he is ruining his time with them.

The ages they're at, a lot of times they can be pretty disrespectful and rude and the younger one often bullies my toddler. As the step-parent, I stay in my lane and if I see something that needs to be corrected (such as really foul language that NO ONE in my house is allowed to use, throwing tantrums, breaking stuff around the house) I will pull my husband to the side and though he understands, he will not do anything because he doesnt want to be the bad guy. Then the oldest son, 17, who lives with us tends to be the "disciplinarian" and that's not fair to him.

It's very frustrating because it feels like we're two separate families living under one roof instead of a single unit. And the kids aren't learning anything in either household.

Any advice, or even someone who can remotely relate would be GREAT.