While nearly all the teen dramas started with main characters who were siblings or would become siblings, every single one did begin with main characters who had some form of absentee parents.
On Beverly Hills 90210, Kelly’s dad took off when she little.
With Dawson’s Creek, Joey’s mother died when she was thirteen and her father was in prison. Jen’s parents sent her to Capeside to live with her grandmother.
Ryan’s father was in prison on The O.C. and his mom kicked him out of the house and soon took off. Summer’s mom abandoned her and her dad she was thirteen.
On One Tree Hill, Peyton’s mom died when she was 8 and her dad spent long periods of time away at sea. Brooke’s parents were often out of town as well. Lucas didn’t really have a dad in Dan.
Serena and Eric’s dad was MIA while Blair’s father lived in France and Chuck’s mom was dead (or so he thinks).
On 90210, Silver’s dad Mel appeared to be out of the picture while Dixon’s biological parents were who-knows-where.
Almost all these “absentee parents” led to much drama on the shows. But it’s worth noting that even the “2-parent households” had their problems, too!
TeenDramaWhore 
Well if we’re talking about at the very start of “Beverly Hills, 90210”, then Silver’s mom was out of the picture, too. I think he went to see her with his dad on Thanksgiving in the second season, but other than that I don’t think he had that much contact with her until he found her homeless in season 5(or was it 6?). Does that count as an absentee parent?
And also, while Steve had both Rush and Samantha Sanders in his life, they were divorced and he was adopted, so his birth parents were MIA too(until he found out his story years later…).
Dylan’s father went to prison early on in the show, and his mom lived in Hawaii so he never saw her except for visits.
Actually, David lived with his mom, Shelia, when the show started. In season 2, it was Christmas when Mel and David canceled on Jackie and Kelly due to Shelia and she was still living in BH at the time. She later decided to move to Portland and David stayed behind with his dad. Then there’s the season 5 storyline of him finding her in Portland living like a homeless person because of her severe manic depression.
Great point about Steve’s birth parents.
I didn’t mention Dylan’s father being in prison because he wasn’t in prison when the show started, which is what this post refers to: the status of the parents in the beginning, specifically the first one or two episodes of the series. Good call, though, on Iris being in Hawaii.