DS just turned 5 months on Saturday. He sits up assisted just great, but doesn't sit unsupported yet. Whenever he's in a reclined position he tries really hard to pull himself up into a seated position (great ab workout, DS!) and is almost successful. When he is seated in our laps or the bumbo, he tries to straighten up so he's not leaning against anything, but then he topples over if we don't catch him quickly enough. I know kids do it at varying ages and I'm not worried about it, but he tries so hard I was wondering if there was anything I could do to help him. On a side note, he's not a big roller either (only rolled once tummy to back and has almost rolled once back to tummy), but his pedi said it happens between 4 and 6 months so not to worry about that either; but are these skills related at all?