Yes you can accumulate all the miles of your family members into your account!

I have done this before and I'm quite certain of it because I received the quaterly statement that the points have been added into my account.

The only thing is that you won't get the full amount of points credited into your account. For example, if you fly F, then your own points would be 150%, C class: 125%, Y class:100%

The points that you'll receive from your family members might be less than 100%. I am not certain of this.