My 14.5 year old son is 5’4". He is healthy but doctor says he will be only 5’6. My wife is 5’8" and i am 5’10.5". Why is son so short?
Because he just ended up to get the short end of the dice roll. No, really. Humans vary. That’s normal.
O.K., so the mostly likely height for your son, using the rule of thumb I gave in an earlier post, is (5’10.5" + (5’8.0" + 5.4")) / 2 = (10’23.9") / 2 = 5’11.45". So if your son will be 5’6.0" when he stops growing, he will be 5.45" shorter than the rule of thumb predicts. This is unusual, but it’s not that unusual. It’s not a one-in-a-million thing. I don’t know the exact figure, but I suspect that it’s about a one-in-500 thing. That’s not usual, but in some sense it happens a lot.
Suppose that you say to yourself, “I wonder if I can get a dice to come up 6 four times in a row.” You throw a dice four times. Each time it comes up 6. That does not mean that this is a bizarre coincidence that could never happen. It happens one time in 1,296. Many things happen to you each day. Some of them seem a little unusual. That’s what you expect. When many things happen every day, a few of them will always seems a little unusual.
Did you ask the doctor if there is anything medically unusual about your son’s height? Did he say that there isn’t anything medically unusual? Then you got a medical opinion from a professional. There is nothing wrong with your son. His height is a little shorter than average, but so what? Why are you worrying about height? Why do you think it matters? Do you think that there’s something wrong with short people just by definition?
The genetic basis for the quite normal variation around the mean expectation is because height is a polygenic trait. It’s influenced by many different loci (a locus is the place in the genome where a particular gene is located; that gene may have different versions called alleles). If both Mom and Dad are tall, they might each have “tall” alleles at 70% of the many loci that influence height, but not necessarily the same 70%.
Children inherit half their genes from each parent. So a kid from these parents would expect on average to end up with “tall” alleles at 70% of loci, and to be in the same population height percentile as the parents. That’s the basis for the calculation of expected height described above.
But (to simplify slightly) it’s a separate toss-up at each locus. So a child could end up inheriting more of the Dad’s genes in the 30% of loci where Dad has “short” alleles, and more of the Mom’s genes in the 30% of different loci where Mom has “short” alleles, and end up by chance with “short” alleles at (say) 40% of all loci that influence height, making the kid shorter than the mean expectation from those parents.
I’m just under six feet, wife is 5’5”. Oldest son is 6 feet, youngest 6’3”. I do have a friend who is significantly shorter than either parent (probably around 5’2”).
That is always true.
I don’t know what you mean by “just under six foot”, but I’m going to assume it means 5’11.5". Using my rule of thumb, the expected average height for a son of you and your wife is (5’11.5" + (5’5.0" + 5.4")) / 2 = (10’20.5") / 2 = 5’10.45". So if one son is 6’0.0", he is 1.55" taller than the most likely height. If the other son is 6’3", he is 4.55" taller than the most likely height. So the first son is very close to the expected average height and the second son is somewhat taller than the expected average height, but he is still not that much taller than expected.
My parents were of average height for their respective genders, and I and all of my siblings, save one, ended up average height. That one out-lier was my younger brother; he grew up to be a towering 6’8". We kinda wondered about him after he grew so tall, but one day my mom dug out an old photo of her father and his brothers from around the time she was born. My maternal grandfather, who I remember being a bit shorter than average, looked like he was standing in a hole next to his brothers. I’d never met any of my granduncles from that side of the family, so this was very interesting to see. We all had an “ah-ha!” moment when we saw that old photo. 
It’s not immediately clear to me what your conclusion was. Presumably you’re saying your grandfather’s brothers were unusually tall, not that your grandfather was unusually short?
It was obvious that there were tall genes in the mix, but my grandfather had not expressed them. He just passed them on for my brother to eventually inherit.
Got it, yes, I was just being a bit slow in reading comprehension. So many genes are involved in height determination that absent rare mutations like achondroplasia (a growth factor gene) it’s usually to complicated to work out precisely what’s going on. But if you’re looking at a situation like you describe with extreme heights in some and not others, rather than more of a smooth distribution, it seems very likely that the same unusual genes are involved for your great uncles and brother, with dependence on something else for expression of the phenotype.
I am 6ft. Mr.Wrekker is 6ft3in. My 2 older kids, b. and g. Are both 6ft and change. The lil’wrekker is 5ft2in, at 19yo. Did we get the wrong baby at the hospital?
Assuming he is healthy, your son still has plenty of time to grow and reach your height and perhaps exceed it. Many males don’t stop growing until their early twenties. This is especially true if he started puberty late. Another sign that he has a lot more growing ahead of him is if his legs are unusually long compared to his torso. The torso grows last so he could grow significantly in torso length.
The shortest person alive is a man. Do the maths.
My middle daughter grew 4 inches her freshman year at college. She was 18yo. Doctor says it happens sometimes with girls. I found it strange.
My adult son is not taller than I am. QED
More interesting question: If you are 5’3" and your son’s father is 5’2", how can his mother 5’? Are you not his mother? I thought you were 5’3".
Pronoun mismatch. The “he” in “his mother is 5’ and his father is 5’7” " is the father. So the two people with those heights are the grandparents.
I will say that boys** like** to grow to be taller than their mothers.
No, they do not.
There’s a formula I read of, when my kids were young, for estimating your child’s adult height based on the height of the two parents, then adding something for boys and subtracting something for girls. IIRC, whatever the results were, my kids came in pretty close to that.
But… I’m 5’11 and my husband is a few inches shorter than I am. My son is an inch or so shorter than I am - hence the “no” above.