You can't. What you can do is set and enforce consistent rules of behavior for all kids in your home. Part of that are age appropriate privileges. SD16 will benefit from this by being older while SD13 will have an example to aspire to. This will also give you a chance to have age appropriate time with SD16 that SD13 should not have the privilege of experiencing for a few more years.

Set the rules. Enforce the rules. End of problem. SD13 complies with the rules of suffers the consequences. The same applies to SD16 of course. Consequences are behavior based and you are not hurting anyone. They are hurting themselves.

Pretty simple.

I have the issue with my older skids. I LOVE my 9 year old SS and would love to spend more time with him, but can't stand being around the other ones!

I have two biological daughters who one or the other hate each other. They're 24 and 26 yrs old !!
At first I tried everything while they were growing up. Oldest always being jealous of the youngest.
So, after they became adults I thought it'd end. No, it didn't.
Now, oldest wants me to not get along with or talk to her sister. Also, even one time denied all of us for my birthday to go out with my 3 grandchildren who are the oldest.
I was so upset.
I tried talking to her. Youngest daughter also apologized to her again. Nope. But, when BGrandfather came on Sunday to get the GC for church. The youngest still was able to see GC. So, that didn't make me feel better.
I can't do anything right, say anything right to my oldest daughter. Never had.
It's frustrating....
Sorry I have no solution for you. Just sharing same thing about my own daughters . You're not alone