my 21mth old stopped overnight feeds around 13mths, didn't sleep through (consistently, I'm sure he did some random nights here & there..) until around 14 months. however he still goes through phases where he wakes at 2/3am, even now. I just bring him in to my bed. I'm too tired at that time of night to try & resettle. I stressed a lot more when he was younger about how much he 'should' sleep, but honestly - they just do their thing. yours will sleep through eventually, when they're ready. 6 months is still quite young to sleep through, in my opinion & experience.