To take a family photo in The Sims 4, you need to disable Autonomy and have your Sims stand in the same area. Wait until everybody looks in the same direction or have an OK pose and snap the photo.
What I like to do is have my Sims seat on a couch, and then have the other family members stand behind the couch.
For example, get the kids to sit on a couch and the parents to stand behind them. You can also bring the pets to the picture.
I admit it usually takes a few tries until all my Sims go where I want them to stand.
If you use the “Take Photo With” option, you can only have three Sims at a time in your photo. If your family consists of more than three members, you can’t use this option to take a photo of all the family members.
Have a photographer take the family photo
You can also add another Sim to your household and have them take the family photo. Get the family to do something together and have the guest take the pic.
Once the photo has been taken, you can move the other Sim back to their original household.
After adding another random Sim to your household for the sole purpose of taking a family photo, you can max their Photography skill to ensure they take an excellent photo.
When you send them back to their household, they’ll charge you 200 Simoleons as a photography fee.
Use a mod to take a family photo
If you want to take a nice family photo that you can proudly hang on the wall, you can use the Pose Player mod. This mod lets you bring multiple Sims into a photo and take a nice group pic.
Using Pose Player is not that straightforward. You may want to watch a few YT tutorials on how to use the mod after installing it.
Happy Simming!