I play a long legacy town, and I completly organize for inactive and active sims with whom they will be partnered.
As most of sims are "maybe" related to each other it is absolutely not easy to check this with any of MC filters, its not deep enough and not easy to follow what relations they really have.

So here is how I do it now (you can also do it with less sims, other ages...)
This is an example for finding the right couples and in addition the future next Baby Generation

1. Mastercontroller -> Sim -> Basic -> Export Genealogy
   Filter
   Type of Sim (Or) -> local
   Age -> Teenager
2. Of course you need to count if all female sims could find a male sim, if not you may need to create a new fresh sim later in CAS to move in -> Make a note of all names you need for later testing
   -> then submit and immediatly switch to your documtent sims 3 folder to rename this scriperror file
   to like _FamilyTree_Teens.ged
3. you need the free App "My family tree" ( I tested a lot programs, but this is the best for the results I need)
   https://chronoplexsoftware.com/myfamilytree/
4. right-click the new ged file and use "open with" My Family Tree
   depending on your system language it can be that you will be asked about the file language, change it to UTF8 windows or what else is right for you, you can see the look of the result directly
5. Now go to Tools -> Relationship Calculator here you compare two sims if they are blood related or not
   Enter the names of two sims from your noted list, it will directly search while typing, so its very easy.
   and will see the what relation they have
   https://chronoplexsoftware.com/myfamily ... ulator.htm

So now you can test all your sims and can organize it easily, also without having to be in the game

And if you want to plan their the descendants, the next babies:
- choose Tab Family -> Family
- type in the name of one of your teenage sims
- add spouse relationship -> connect to existing -> and choose the one you figured out best match
- add child now -> but here "add child relationshipt" so it is connected to your sim couple
- repeat with all teen couples

Well now look up "unknown" in the Relationship Calculator, from the last name you know who is who, test and make a note again.
You can also give them real names. Only remember that when the teens marry the last name changes too.
You can also find out for them with whom they are too near related to better not be partnered in the future.
This is the plan.

Done, you also know now if you maybe need new created sims too to make your town grow healthy.
You can also export your changes to a new ged file.

I know it is only a game and this is in the end not relevant, but I get a lot of FUN out of it