Estate Planning for Almost Here Babies

Hi Liza,
I am about to create my Will and Living Trust.  My son has two sons and his wife is pregnant with twin girls.  I would like to know if I can name the twins in my Will/Trust now although they are not due to be born until December? I’ve written Wills that name children soon-to-be born. You could say that you want to benefit all of your son’s children, including the twins girls due in December. Or you could just say all of the children of your son that are alive at your death (which, unless you die before December would certainly include the new twins). Good luck!