fix for if your Sims 3 Game freezes @ relationship screen in Create-a-Family
I have found that what seems to be the problem is custom content somehow prevents the family portrait from appearing, and the game gets stuck trying to load it. So when you go to create a family, make some Sims but don't make them look how you want them! Don't customize their appearance yet, don't touch that.
Just go with standard, random Sims whose faces appear properly in the little squares at the bottom of the screen, give them the names, gender, traits, relationships etc that you want then go ahead and finalize your family and move them into a house, start playing that household. To make them look how you want them to look, there are two options.
If you don't care about body size, face-shape, muscle-definition, chest size on females, etc, or you like the size/shape/etc the game already generated for you (you can change this in game, by going to the Hospital and getting Plastic Surgery for your Sims, but it costs Simoleons and there's a possibility for the doctors to mess it up and you not getting to customize and having to try again) just use a dresser to choose their outfits, and a mirror to change their hair and put makeup on them, and you're good to go.
If you do want to choose their body size, face-shape, muscle-definition, chest size on females, etc. then, once you're in, press Ctrl+Shift+C and type "testingcheatsenabled true" and press Enter. Now you can Shift+Click each Sim and click "Edit Sim in Create-A-Sim" and customize them however you want without fear. Any comments the game may make about the household (deleting and canceling if you cancel the modifications for instance) won't actually affect your Sims, it's only saying that because... I think, it's the same interface used for the creating of families, except that in this case it's only editing the individual Sim because of the cheat.
All I know is, I swear by this and do it every time I'm making a new household.