You bet that testiculer temperature is directly related to fertility.

As for the pilot's extra male children, this is due to LACK of ejacjulation. It seems that if a male has a lot of orgasims, he produces lotsa X bearing sperm thus girls. Infrequent orgasims produce more Y bearing sperm, thus male children.

Quite frankly we do not have enough information to make much more than guesses.

This much we know: if you want kids, wear a kilt and have sex. Which seems to be a good idea reguardless.