1st Egg Today, but is it fertile?

[Buns]

I have seen no breeding by our self blue Dutch rooster. His hen layed her first egg today... plan to put it in the incubator anyway, but shouldn't I be seeing him breed her? They are penned together like many of my other birds and I am aware of breeding activity of all the pairs with the exception of this one. Roo is very very sweet and seems kind of immature behaviorally compared to the OEGB's I have. Appearance-wise he looks mature, he is the same age as the hen.
Thank you.

 

[bigspringshatchery]

It could be fertile. But it's wise to wait about 2 weeks before trying to incubate any eggs. Let the girl get the pipes worked out. You can try but the eggs will be small and you also could get a double yolker.

 

[Buns]

Thank you for your reply.
Why would it be more likely for an early egg to have double yolks?