Issues with sims FreePlay

It’s the “Allow App to Track” or however it’s worded. You have to click allow or the game won’t work. I had the same issue when I transferred my game to a new device. I always say no to any kind of tracking but Sims Freeplay says we have to click allow. You probably need to reinstall the app. When you do it will ask near the very beginning in a box “Allow app to track” answer “Allow”. Once you do. It will work. 
Your other problems with the babies is way over my pay grade but someone will be along to help you that will know what to do. Someone allows does. 👍🏻😊

For the family issue:

There was a post a while ago, but now it’s buried somewhere.   
  
You need a free slot for a new Sim and some LPs. Use the simtracker to add a new Sim to the infant’s home. Then call the mom or dad to the home and be nice to the new Sim until they can ask to move in.  (If the parents are married, they need to divorce first, but the relationship can be built up again pretty fast.)
When the first parent moved in, you can move the new Sim to a different lot or out of town. Now call over the other parent, if needed build up the wanted relationship and let them move in, too. Voila, the family lives together again :) 

Edit to add: It looks like only 4 Sims can live in one home in your town. You can unlock more while progressing in your town :)