In Kate's own book about getting pregnant with those 6 babies, she says she had to talk John into it. He thought two kids were enough and another procedure likely to cause multiple births was just too risky.
I think she has always been pushy.
As far as her constant whine that she is just trying to support her kids, bull. Just trying to support your kids does not mean living the lavish lifestyle she has come to lead. She could get a normal job and lead a normal life, but she has no interest in giving up the limelight.