WOW. Being a grandparent must be way cool. I am looking forward to the year when I am a gram, but hopefully that will be a minimum of 10 years from now :-) since my oldest former wee one is only 19. And as for wee ones birth size corelationing to adult size, not always. The aforementioned 19 year old was 10 pounds, 5 ounces and 23 inches long at birth (that's about 4.7 kilos and 58.4 cenimeters for those who are metric) and he is now about 6' tall, and 160 lbs. Not puny, but not big, either.
And Big Mick, I have long since been replaced as a fishing partner by my kids, I hear grandkids are great fisherpeople!