When can young Roos fertaliser eggs?

[Pent]

Possibly in the wrong section but...
I have two mottled houdans cockerels, spurrs are growing and they're finding their crows, and I have a super broody maran. If I put the boys with the laying hens, how old do the guys have to be before I get a fertile egg from them? I can't keep them forever, I live in a neighbourhood not on a farm, but it would be cool to get a few chicks before they go.
Also sorry about the title, autocorrect and I can't seem to fix it.

 

[Judy]

The spurs don't really tell you much, but the crowing, plus some reddening up of the comb, and perhaps some slight pink or red color to the legs, are indications. An average age is probably 14 or 15 weeks, but different breeds vary in how fast they mature, and I've never raised that breed or a similar one. One sure way to tell the egg is fertile requires cracking the egg (the only other one is to incubate it and get a chick

https://www.backyardchickens.com/t/16008/how-to-tell-a-fertile-vs-infertile-egg-pictures/0_20