Arnold is a business man and wisely he is spreading the risk of his children being twinks.
We see now that it has paid off, this one beats the fat one already physique wise.
LOL.... Seriously from what I heard the kid plays baseball,soccer,cycling is a bully,joker etc just like daddy LOL.... Looks like by the time he hit 18, he'll be taller than Arnold.... Wouldnt be surprised if he takes bodybuilding and open up his own gym/health club.... can you imagine the $$$$$$$ + popularity? .... I think Mildred has.
Btw, Mildred (the maid) kinda looks like a younger version of Arnold's tough mom Aurelia... so is a win win "genes" situation for the kid..
This is how I picture the boy in few years