Is it unusual to have multiple basal cell carcinomas before the age of forty?

Yes: Assuming you have had a normal amount of sun exposure it would be unusual for multiple basal cell carcinomas to develop at this young age.

Yes: But, unfortunately, it does happen in people who refuse to protect their skin from the sun.

Depends: Usually a history of multiple basal cell carcinoma (bcc) indicates a genetic predisposition towards tumor development. A known genetic mutation can lead to multiple bcc, small pits on the palm & other findings. This is known as basal cell nevus syndrome or gorlins. Some patients are thought to have a milder form of the disease which only leads to increased bccs. See a dermatologist/mohs surgeon.