Staying in the upright and lock position

So my boys at almost 7 months will sit up on their own as long as I put them in that position. Im so happy we finally hit that milestone. But as far as crawling they really don't want and part of it. They'd prefer to roll to their desired destination. :) Although Ethan would now prefer to stand up and he flies around in his walker in all directions. Parker can do it too only when he isn't lazy. Lol I just can't believe they will be 7 months old on New Years Eve!! Where has the last 7 months gone?????