Ref. 23:
This reference (in English) is a synopsis of the original study by Bailey and Pillard that was subsequently proven to be wrong and even a fraud.  Notwithstanding this, the report is still referred to by many homosexual activists as “proof” that homosexuality is to a large extent hereditary.  Translated into your language the synopsis reads (in part): 

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Of the relatives whose sexual orientation could be rated, 52% (29/56) of monozygotic co-twins, 22% (12/54) of dizygotic co-twins, and 11% (6/57) of adoptive brothers were homosexual.

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For a look at the original synopsis in English, click here (file size 192 k)