There is a שיטת ראשונים [the ר"י ברזילי] that a father can be מקדש his son who is a קטן by means of זכיה.
The Gemara [Kiddushin 19] asks if a father can perform ייעוד [marriage w/ his אמה עבריה] for his קטן son. The Gemara says NO WAY b/c if he can then מצינו אישות לקטן and that can't be?!
Why can't that be? Just like a father can marry off his son מדין זכיה he can also perform יעוד?? It seems that the Gemara rejects the whole notion of a קטן marrying.
Then the Gemara asks that since we need מיעוט to teach that one who sleeps with an אשת קטן is פטור ממיתה that indicates that there IS יעוד לקטן [b/c otherwise how does a קטן have a wife]. How does that prove that there is יעוד לקטן. Maybe the מיעוט relates to a case where the father married her off to his קטן son and not יעוד?!!
