It's called the fraternal birth order effect. You can do a google scholar search on it. There's no exactly determined cause of it, but it does seem to exist. And it doesn't say that you WILL be gay if you're male with x number of older brothers, it's just more likely.
There's actually some evidence that prenatal hormone exposure can have an affect on later gender identity and sexual orientation. For instance, in the case of XX girls who are born intersex from an excess of testosterone in utero, they are more likely to be lesbians and exhibit more typically male interests (like drawing trucks instead of flowers at a young age). You can absolutely debate the point, but there is some evidence to support it.
Hi there. OH goodness. No. Not true. Not at all. For men or women with two older same sex siblings. good luck
There's some evidence that boys born after other boys in the family are more likely to be gay, but it's certainly not proven, and still not likely. There are a number of potential reasons for it to be true, but that doesn't mean it is. One theory is that hormone levels are different after having multiple boys, and it's only thought to affect boys because of stuff to do with developing boys having testosterone around. Another thing is that there are more second and third born boys than there are first borns (you only get one first born, but you could have 3 other boys after that). Therefore, there's a larger pool, and you would expect to find a larger absolute number of gay people in that. Finally, there could be social factors that might contribute to the development of sexuality in later boys, but the social influence is controversial all by itself.
tl;dr: No, there's no reason to think that younger sisters would be more likely to be gay.
I'd have to see this 'evidence' other than some odd theory someone has come up with. Birth order does not have anything to do with sexual orientation. Testosterone also does not dictate sexual orientation.
I'm one for science and this is not science based.
Luck to all and sexual orientation isn't so simple to define as which number kid you are to a family.
My father had a lot of sisters and brothers and none of them turned out to be gay.
I am the eldest of 5 on none of us turned out to be gay. There are 3 girls one after the other and two younger boys.
My sister in law has 2 girls and the youngest is a boy, he turned out gay.
The question can be is it nature or nurture?