Technically, it's possible, but they're pretty far from humans.
You can achieve this via a rather convoluted genetic mechanism. However, the resulting species is majorly different from humans in terms of reproductive mechanism. Your question kind of requires this.
The following conditions would create the effect you want:
* The information related to subspecies is stored on the X chromosome
* Female (2 X chromosomes) embryos are not viable and die in the womb without exception. This is because vital information is stored on the Y chromosome.
* Both races are hermaphroditic, but the hairy race develops either one set of genitals or the other randomly in the womb, like a birthmark. This information is stored on the X chromosome.
* Both races produce egg cells with both X and Y chromosomes, but the X chromosome is necessary for egg development, so the ones with Y chromosomes die immediately.
* Sperm cells, however, can survive without an X chromosome.
* The X chromosome is really heavy, due to all of the extra information stored on it. This means that sperm cells containing an X chromosome are too heavy to swim as fast as the Y chromosome sperm. 1008
This ensures that virtually all babies are born XY.
The effects of this are:
* Every child gets the XY genotype, making them all genetically male
* Hairy fetuses develop either testes or ovaries (maybe these organs are in the same place, so only one can form?), which produces either female or male hormones, depending (the alien equivalent of estrogen and testosterone). This means that they appear and act either male or female, despite being genetically male
* Tentacle fetuses develop both sets of sex organs
* When members of different species mate, the mother is the one that provides the egg cell. This cell contains the subspecies-determining X chromosome, so the mother's race is taken on by the child.
* The other chromosomes determine the other aspects of the body appearance, so both parents give DNA.
Possible issues with this:
* Fertility is a little lower than in humans, because embryos with XX die in the womb.
* Birth defects in the hairy species are common, where both sets of genitals manifest on top of each other. This probably leads to the fetus dying, but that's up to you, the author.
I can't see this happening by natural evolution: there are too many difficulties on the way there. More likely, they were created by genetic engineering. Maybe a species found a better way to adapt to their environment, say learning to space travel, by messing with there genes, and they created this? 1008