QJ, I dunno.... brother/sister breeding pairs sounds pretty inbred to me.
I am thinking Squeak is a girl more and more too. She really has more volume than the other two boys, has no whistle quality, and keeps reminding me of a muted honk or fog horn. Either way, he/she is a keeper!!
Here read this.. and then ask Celtic since she breeds for realz.
https://www.backyardchickens.com/t/409262/is-it-ok-for-ducks-to-mate-with-brothers-and-sisters
Agree with the no whistle quality. What do you think about my deal I posted about the high pitched squeak?