The game should have created bassinet for the 2nd baby. Have you tried going into to build mode and placing a 2nd bassinet? Then do a save as and exit the game then reload and return to that lot to see if the babies get put in separate bassinets. One other thing I can think of is if you are using a CC bassinet, that might be causing it so if you are, you might try removing that from your mods folder to see if that clears it up.
You could also try moving the household out of their current lot and then back in to see if the game will generate a bassinet for each baby.
Hope this helps.
Thank you for the advise I'll try the cc bassinet, because the other suggestions didn't work.
