Don't know if it's sex but some varieties of Asian Pears need another
variety close by to have good production. Same as some apples. You
can find out which varieties grow well together.

Having 2 trees of the same variety won't do much for you.

Ginko! Now there's a tree where sex counts. It takes 20 years before
trees bear fruit. Many cities planted them without knowing the sex
and decades later ended up with a stinking mess. These days nurseries
graft from known male trees so there won't be any stinky fruits.
Smells like dog shit.