A child of human/drow half elf and human/nondrow-elf half elf is a half elf.
It would look like a half elf with 1 drow feature (skin, hair, or eyes).
Nice! Thanks. In this case though i thought of making the father not human, but a normal half-elf (father human, mother high elf) and mother drow.
Moi? Serious? D&D is for fun.
It's your character, you make him up how you like. Scope for an great backstory, though. What background will he have?
His human grandfather abandoned his grandmother and she never forgave him. He's probably long-dead by now but the grandmother blames your PC anyway for being male ("all men are like your grandfather") and this makes him defensive. He over-compensates for his insecurity by becoming a brash and reckless adventurer. He has a "thing" about female trees, which could be interesting if you make him a druid.
Something like that. Go wild. He's your character.
My initial idea:
His father was a stereotypical half elf, (wonder lust, no roots, had adventuring pretty much thrown, if not forced on him), he was working as many things in life, mercenary, soldier, diplomatic envoy...
His mother was a drow exile. Ambitious, energetic, uncompromisable, but ultimately doomed to fall with the rest of her city and house. Fleeing the Underdark for reasons she would never reveal in full (except the destruction of her home, but not why, when or by whom), she came to the surface and leaved on the outskirts of civilization for a long time, working along bandits, rogues, rangers and other similar ilk.
The two met while he was doing official "business" for the authorities, investigating smuggling operations and demi-human activities in the border regions. Her group (or what was left of her) were chased by war band of invaders and stumbled upon the patrol the father lead. They were forced to work together and eventually they were the only ones that survived the skirmish. Him being a half elf, and she a drow, they had enough time to adventure around and adventure they did, both as pair/duo and as parts of larger parties. In time they became powerful and influential individuals, developed a romantic but turbulent relationship, but she always remained in the shadows, both because her presence would jeopardize their future political ambitions and because of the unseen threat that she appears to have been running from still.
Eventually they settled down and he got a ruling position as high level crown-backed duke with their own castle and estates. All seamed to be going well, they had a son and he was growing strong and capable. They were rich, respected and influential, until one day, after the father and the son returned from a diplomatic ambition, and found the drow mother on her death bed, dying from a fatal wound. This lead them both on a vendetta quest to find her assassins and avenge her death. This lasted a long time, lead them to may foreign lands even venturing the Underdark, and when it was finally over, they found themselves exhausted. Both emotionally and economically.
There was still enough prestige left for their powerful friends to help them start a new life, but the father has had enough of politics and warfare. On top of all that, he feared a possible revenge from their Underdark enemies and retaliation against his son. So they decided to abandon their estates and names, and when into the wild. They ranged for some time and eventually came across a small woodland community. They became the local ranger-protectors. The local population was not numerous and among them was a family of an elven wanderer and a human wise woman. They in turn had one daughter (half elf). Eventually the son and the daughter married and had a son of their own.
It is this child that i intend to play with. He grew up listening to the stories about his ancestors, but was especially impressed with the stories about his paternal grand mother. In her honor he took up the worship of Eilistraee, in good will and hope of redemption for all, especially the drow. Living among a small mixed population wilderness community might have helped this. This idyllic life was not to last, alas. Someone in the community (or so it seamed) betrayed them to a dragon cult and the entire area was desolated, it's population massacred. Only he and his father survived finding nothing but burning remains when they came back from what appeared to be a routine skirmish with a bordering goblin tribe. The PC then decides to track down the dragon cult, investigate the matters and take what ever action is possible, or necessary. He still has a benevolent mind, but recent experiences have made him less trusty of others. This conflicts his previous ideals of Eilistraee somewhat and is a base for a personal conflict in the future.
Sorry for the long post, but once i started, i just couldn't stop
Waaaay too general. There are already huge variations in appearance of humans, drow, sun elves, moon elves, wood/wild elves, aquatic elves, etc. A better question is - what can't he look like? A human with black skin who has sex with a gold skinned sun elf can have a black skinned half-elf kid, nevermind that there's no drow in the blood.
You can have pretty much any ethnicity of human, mixed with at least two elven races (yes, some elves have green hair). At that doesn't touch on the fact that the elves themselves could have mixed blood as well in their past that could show up. Drow tend to be uniform in appearance, but that's because they're generally portrayed as racist bigots that play to the whole purity of blood angle and kill children that don't fit a narrow stereotype, though there are exceptions. The rest of the elves tend to be more open minded.
The grand father was a child of a one night stand between a dark haired human stranger with brown eyes and elven maiden from the high forest. The grand mother was drown with silvery white hair and obsidian skin ., but lost the red shine in her eyes because of the long time spent on the surface. Even her skin got to turn more whitish and purplish over time while her eyes went deep lapis blue. His maternal grand father was a wood elf with dark blonde hair and green eyes while his maternal grand mother had sky blue eyes and red curly hair.
P.S. Thanks for all the helpful tips so far guys!