Not a left hander, doesn't fit. I'm a "equal hander" with preferences.
I have heard that years ago. The problem with those studies: Sometimes the scientists forget to check a second group, to check how many lefthanded oldest sons are straight.
Just take the "no older brother" thing.
So they have found out that most gay men supposedly don't have older brothers?
What a surprise! In "three children at max" societies like you have them in the West, most men don't have older brothers. I have just checked it for Germany: 1,8 children per women.
Today people only have one or two children, so the probabilty to be the oldest son is significally higher than being the second or third oldest son.
Firstborn a boy: 50%
Secondborn a boy: 25%
Thirdborn a boy: 12,5%
So to have three boys in a row is only a chance of 12.5%
You can add a girl to that, though that would not change too much.
If I take 500 women with 1000 babies (2 children per women) that's
250 fristborn boys + 125 secondborn boys with older brother + 125 secondborn boys with older sister; 250 firstborn girls + 125 secondborn girls with older brother + 125 secondborn girls with older sister = 1000
So only 125 boys of 500 have older brothers, while 375 boys have none. Seems like somebody needed a publication.