What is a daedra compared to a mortal?
The short lore answer is, that lesser daedroths are one subgradient higher than mortals.
In addition they have certain advantages, which are connected to being a subgradient higher (like e.g. immortality - which "mortals" gain if they advance in subgradient, read CHIM or other forms of apotheosis).
Now what is a subgradient? It's a level of existence.
In a way the Elder Scrolls world is like a pyramid. At the top you've got the godhead, who fractured and created the aurbis. Which split into Anu and Padomay. Which split into greater and lesser concepts aligned to these overlying directions (these are the et'ada, original spirits). Some of the et'ada sacrificed parts of themselves to create a world, while other did not. This divided the et'ada into Aedra and Daedra.
Now mortals are a subgradient of the et'ada, the Aedra to be exact.
Thing is, the line between mortals and Daedra are thin. "Walk like them until they must walk like you", also known as mantling. Likewise they are other ways to get to a higher subgradient (CHIM, apotheosis, among other). Examples would include (but are not limited to) Vivec (CHIM after false apotheosis), Tiber Septim (mantling, CHIM), CoC (mantling, apotheosis).
Now that's the metaphysical side of it.
The practical side is far easier: If it procreates with other members of it's own kind, the species in question isn't daedric. Likewise if it souls go to the dreamsleeve (the dreamsleeve is the "soul recycle bin" for souls aligned to Nirn as their aligned AE) or to another aligned AE, it isn't daedric.
Baliwogs and Gnarls and Grummites and Scalons procreate, therefore they are not daedric. A vampire's soul, when slain, will go to the Dreamsleeve and not the waters of Oblivion, therefore a Vampire is not daedric. An Ogrim's soul will be banished into the waters of Oblivion and not go to the dreamsleeve or an aligned AE, therefore it is daedric. Umaril's soul went to it's aligned AE and not the waters of Oblivion, therefore he wasn't daedric. Similar to the tortured Mythic Dawn members you meet in Camoran's paradise: They also went, when killed, to their aligned AE, which was Paradise. Bad luck.
There isn't something like being "part daedra", it's a state of being, not a question of genetics.
Hope anyone is able to understand this .