My daughter who just turned 35 on the 19th, was shooting when she was a year and a half She could walk when she was 7 months old and run when she was eight months old. i made her a longbow from a single piece of bamboo with a maple handle, it really shot nice. In two months she had perfect form and good hit milk jugs with small htm tipped arrows at 10 yards nearly every shot. one day in the house when she was about a year and 10 months she said i shoot the elk. before I could stop her she did right in the boiler room. the elk was a painting hanging on our living room wall.
I started my son about the same time. he had a little fiberglass bow. for his second birthday his gramma gave him a blowup boxing rabbit. I blew it up and showed him how it would not fall down. Puzzled he walked away, a few minutes later he came out of the back porch bow and hand and arrow on the string and said "I'll fix it" and wham right in the heart. My mom nearly died of a stroke laughing as the rabbit deflated and died.
with my grandson I got him a Maddog for his fourth birthday. the first thing he did was show us how far that little bow would shoot. right off the 5 acre yard and into the neighbors yard. when he was at our house, i let him shoot the sharp arrows into my target that came with the bow. while I was getting the arrows from the target, he put an htm tipped arrow on top of the neighbors garage and another, before I could get him stop, over the other neighbors house. Keep an eye on those little ones. They are quicker than you may think.