Male tortoiseshells are very rare.
In order to be a tortoiseshell, a cat needs two X chromosomes for the black and red pigment to mix. Males have XY, so they can either be red-based or brown-based. I don't know anything about cat genetics so I might be wrong.

It can happen though. But a fertile male tortoiseshell is also near impossible I believe.

I saw an article about two male tortoiseshells. You know they're rare when there's an entire article about two.

* Ay again, cat genetics, don't really care. I have like 6 male tortie OCs now because they're pretty and fun. Ignore cat genetics, transgender your cat, give them a story about being infertile but wanting a family, go crazy! This is warriors, nothing makes sense! We have bright yellow cats now!