Maybe it's a hybrid, of two species ? You've made no mention of it's origins..., if bought & grown from fruit with seeds, or instead, possibly from someone that has a collection of different varieties, or how you ever came to obtain it. As a seedling, or rooted cutting, or much else information, to go on, other than mainly just a photo.
If somebody had two plants of different species, or one was a hybrid, , in flower at the same time & a big bumble bee came along & visited two different flowers & one produced a fruit & the seeds were harvested & grown, well then it just may be a hybrid. A nearly mature fruit helps out, with I.D. to be more certain...
Some are hybridized, intentionally, just in an attempt to get an improved looking flower, or more fragrance, or may produce a fruit & then sow the seeds, or simply created by "open" (cross) pollination, of different ones. Some people grow Passiflora , just for butterfly to lay their eggs on & not always just the flower or to harvest the fruit.
I had P. 'Incense' many years ago & a bee came by, as it was so fragrant & after I saw that..it produced a ripe fruit & seeds, possibly with pollen, from local, wild ""Maypop"...
