I've watched literally dozens of let's plays, listened to dozens of opinion pieces and read thousands of comments in threads, but one thing has always struck me as odd and, frankly, disturbing. Not ONE single person has asked about Sarah's Mother, and I'm not exaggerating ... not ONE. Doesn't anyone else find that a little disconcerting? Here's my take on things, although this really isn't the reason for the thread:

We see Sarah's bedroom which gives us an immediate impression of what she's like. She's clearly a feisty girl with particular and quite individual tastes for a girl. for one thing she plays 'soccer', not only more often than not associated with males but also something not automatically related to the US. She's so commited to it that she's won trophies. You would think they'd have gone for a sport more associated with the US, but clearly they chose this deliberately. We also see a typical teen movie poster, showing her ordinary side.

On the bedside cabinet there's a pic of two women and Sarah. I'd assume one of those women was her mother and the close proximity to the bed shows she loved her dearly and clearly misses her. Every day she gets up she sees a picture of her Mother. On the way to Joels bedroom we see more pictures along the landing. Later on in the story we find out Joel does not like photos that remind him of painful things, something also demonstrated at the beginning of the game by the lack of any photos in his room. So, he respects Sarah's need to remember her mother but doesn't prescribe to it himself.

The Mother has clearly been out of the picture for a while. In my opinion, Sarah is being presented as a girl brought up by a male. Either her Mother wasn't around and that picture was of her visiting or her Mother died.  Joel's inability to cope with grief leads me to believe the lack of a photo in his bedroom means the Mother died.

After we flash forward 20 years Joel is offered a drink. There's something telling about the slight pause in the way he refuses. I think he's used drink in the past to drown his sorrows. Later there's another comment from Joel about suicide when Ellie suggests it's easy. He says 'Trust me, it isn't easy.' That shows he's had first hand experience of suicide. I don't think it's his wife because it sounds far too intimate.

So, Joels wife died and left him struggling with grief, the mortgage and bringing up Sarah as a single parent. He turned to drink and contemplated suicide, perhaps sitting at the kitchen table with his revolver in his hand, but he thought better of it and decided the only option was to remove any reminders of his wife's death. He could not ask his daughter to do the same. When he finally accepts the photo of him and his daughter from Ellie, it's a sign he's come to terms with grief because grief is the absense of something you love without anything taking its place. Ellie has now become his reason to live and he can deal with 'remembering'. His road to redemption is complete.

There's no mention of Sarah's mother when they're driving to escape so I'd suggest it's either an oversight on NDs part or she's definitely dead. Sarah could have asked 'Do you think Mum will be alright?' or 'Do you think it's spread to Argentina?' (if you're right). The picture of two woman and Sarah could be of her mother visiting or Sarah visiting her mother but I feel as if it's a typical family 'snap'; an in the moment shot taken at home.

There is mention of Sarah's mother - in the University chapter during the various conversations between Joel and Ellie. Ellie asks Joel why he never went to University, and he says it is because he had Sarah at a very young age. I believe it went along the lines of "My childhood dream was to be a singer but I became a father early and it changed things."
Since Joel has custody of Sarah at the time of the outbreak, we can assume that the relationship dissolved for one reason or another. Joel seems to have a stable income, and it is possible he won custody in a legal battle. Maybe she was a drug addict or something, or maybe she had a baby really young and didn't end up wanting it, or maybe she died. A lot of possibilities that can stem from young people having an unexpected baby.

*edit*

"Sometime in his youth, Joel had a daughter named Sarah and was married to his wife for a short period of time. Saddled early in life with the responsibilities that come with being a father, he never had the opportunity to attend college. No mention is given as to the fate or whereabouts of Sarah's mother. However, it is revealed in a conversation between Joel and Ellie that the subject of whatever happened is very painful for Joel to talk about, and that he raised their daughter as a single parent for most of his life. "

Joel very clearly has issues talking about people from his past that he has lost tho, he doesn't open up to Ellie for so long about his lost daughter, I would think the people around Joel know that if he isn't talking about something, then it's a sore subject that he doesn't want to talk about.

It's also clarified in the Dam chapter that Joel raised Tommy by himself and struggled with it.

Now it's obvious why he clung to Sarah so much and was so bitter and closed after her death. Everyone in his life died or left him, just like everyone in Ellie's life died or left her. Deep huh?

Rick in the Walking Dead also doesn't talk about his wife after killing her in season 3.. its what the cool reluctant heroes do these days.. Kill zombies, raise the children, never talk about the wife..

And then there is Lee Everett. Kills the man his wife is cheating on him with and tells everyone about it! Even that kid named after an Orange plant

The soccer thing is easy since soccer is the most played sport in the US at junior level with both genders with huge participation rates it is only at professional level where it falls away.

The suicide point could be about Joel's mental state after Sarah was killed and how low he got because a large part of the story is about Ellie and Joel's relationship that changes Joel from cold and closed off from life with no real reason to live, to some one who has a purpose again.

That second part is a good theory but speaking honestly the plot isn't deep enough to have had that thought out. Everything is very hand-holdy and pseudo-choice based, and the plot even shows that quite often; Neil Druckmann wrote a very average, predictable plot that survives solely on the character interaction between Joel and Ellie (mostly the development of Ellie if I'm honest, because Joel is essentially a flat character for most of the game). Sarah herself is just a plot device to give Joel reason to have long term issues that are brought to the forefront by Ellie, and I'm being 100% honest when I say that because of this I doubt they gave any thought to Sarah besides daughter to Joel's single father trope. 

Not at all. Sarah's mom had nothing to do with the bulk of the story.