Is there any way of growing a butt if you were born without one?
Well, there's one way I know to make your butt larger and you can try weight lifting. If you use machines that strengthen the back of the upper thighs then they will also help shape your butt to look larger and muscular.
Growing taller after puberty (18-25 years old) is impossible without surgery or a defective pituitary gland. However, growing shorter after puberty is common, if not universal. In short, the only way to change height dramatically after puberty is through surgical procedure to lengthen the lower leg.
Even if you use weights to tone your butt you won't make it larger as long as you stick with lighter weights (or no weights) and more repetitions. If you were to use heavy weights and less repetitions, that would build the muscle and therefore make your butt appear bigger. Lighter weights and more reps will just tone and add definition.