Hello there! Quite a long post there lol. Looking at the heights you have mentioned including your dad and cousin i would have expected you to be a tad taller ( although thats just an assumption things differ from person to person) so i think you do have a good 2-3 inches left in you tbh. You may be 19 but remember its possible to grow up to 25 ( i think lol)
Basically eat well, exercise, get lots of sleep and you should reach a more desired height. If you are supposed to be 5ft11-6 ft i would think that 6ft2-3 is a perfectly good height to aim for; thats what im currently aiming for now!
Keep your spirits up and keep to a good system and you should grow in no time. Also a piece of advice from me, i would avoid any "Grow taller" pills and other crazy remedies that are on the internet. If your sretches heed no results dont turn to these as tbh they are a load of BS lol
Thats my view on things anyway

Remember staying positive is KEY to height success!