Sam Winchester and Mary Winchester have a mother son relationship. Although, Mary died early in Sam's life, so he didn't know much about her, or what a mother's love is. Sam does care for Mary though, and misses her.
Background
Sam is Mary's second born son, and unfortunately, didn't get to be there in his life. Mary died on Sam's 6 month birthday, in his nursery. Before Azazel killed her, she recognized him, from the deal she made years ago, and finally realizing whats happening. She died trying to protect Sam from the yellow eyed demon. After her death, John raised the boys into the hunter lifestyle. Growing up though, Sam begins to ask questions about what happened to Mary, but didn't get any answers for a while. Sam finally finds out when he learns about hunting, and he too begins helping in the hunt for the demon.
Season 1
| “ | To Dad? And his crusade? If it weren't for pictures, I wouldn't even know what Mom looks like. And what difference would it make? Even if we do find the thing that killed her, Mom's gone. And she isn't coming back. | ” |
— Sam
in Pilot | ||
22 years after Mary died in Sam's nursery, Sam is forced back into hunting by Dean. He mentions Mary to Dean in Pilot when he mentions that if it weren't for photographs, he wouldn't know what Mary looked like. Sam does care for Mary, but he is overall frustrated at the hunting lifestyle.
Then in Home Sam has a vision about their old house. So he and Dean head back to the old place. Unlike Dean, Sam doesn't have much memories in the house, so it doesn't bother him the way it bothers Dean. Later on, Sam gets pinned to a wall by the poltergeist in the house. A flaming figure approaches him, and as Dean is about to shoot it, Sam stops Dean. He knows who it is. Sam know's its Mary. Mary reveals herself to the boys and Sam looks upon his mother for the first time (that he can remember). Mary looks at Sam and apologizes to him, which confuses Sam. Mary doesn't tell Sam anything else and sacrifices herself for Sam and Dean.
Throughout the first season, her death and Jessica's, push Sam to hunting yellow eyes, and fuels his passion for it.
Season 2
Sam at Mary's grave
In Children Shouldn't Play With Dead Things, Sam drags Dean back to visit Mary's grave. The grave itself is just an empty casket and a headstone set up by their uncle. At the grave, Sam talks to Mary, and puts John's dogtags in her grave area. This site is like Sam's only connection to Mary.
In All Hell Breaks Loose - Part 1 Sam finds out via Azazel that on the night of her death, Mary knew the demon when she walked into his nursery. This confuses Sam and puts questions in his head.
In All Hell Breaks Loose - Part 2, Dean kills Azazel with the help of the spirit of John and Sam is stunned that they have finally avenged Mary and Jessica and is at a loss at what to say. Dean, however, finds the perfect words: "that was for our mom, you son of a bitch."
Season 3
Thanks to Ruby, Sam's curiosity is triggered when she mentions about how all Mary's friends are dead. This causes Sam to begin investigating Mary's friends and family. He eventually finds out that everyone he could find was killed off.
Season 4
After Dean gets sent back in the past and meets a young Mary, he comes back and tells Sam about the deal she made that allowed Azazel to come into his nursery years ago. Sam also learns about how Mary used to be a hunter, before she married John.
Sam hallucinates Mary
In When the Levee Breaks, Sam hallucinates Mary in the panic room. When she appears, Sam tells her to go ahead and tell him that she is disappointed in him and that he is a poor excuse for a son. Although she died early in his life, Sam still values her opinion. The hallucination Mary answers differently, and tells Sam that he did the right thing. Sam mentions Dean, and Mary points out that she comes from a long line of hunters, and that their family is cursed, but Sam can use it for good. When Sam asks Mary what if he can't control it due to him being weak and if Dean is right. Mary answers that Dean doesn't know Sam's potential, and that Dean is the weak one. Mary continues on to encourage Sam to kill Lilith and go on without Dean. She finishes by saying to Sam to make her death worth something, and shes counting on him.
Sam is now encouraged by his hallucination of Mary that was probably brought on by the demon blood. With this, he continues on his path.
Season 5
| “ | You think you can have that normal life that you want so bad, but you can’t. I’m sorry. It’s all gonna go rotten. You are gonna die. And your children will be cursed. There has to be a way... | ” |
— Sam and Mary
in The Song Remains the Same | ||
When Anna, goes back in the past to kill Mary and John, Sam and Dean, with the help of Castiel head back in the past. Now in the past, they head over to their old home. When Sam sees Mary, he stares at her, due to the fact this is the first time he has seen her alive and happy. When John leaves, Sam and Dean tell Mary something is coming after her and John. Mary doesn't believe them right away, but they notice John is missing.
Once they have John, and its revealed that they all are hunters, Mary takes them all to a safe house. There it is revealed to Mary that Sam and Dean are her sons from the future. Dean tells Mary about the demon that comes for Sam when he's six months old and that on the morning of Nov 2, 1983 to take baby Sam and run, but Sam cuts him off. Sam says that the demon will find Mary where ever she goes to find him. Sam tells Mary she needs to leave John, which shocks her. This means neither Dean nor Sam would be born. What shocks Mary most is the fact that her own sons are ok with not being born. Sam continues on by saying that her children will be cursed and will never be normal. However Mary tells them it is too late as she is already pregnant with Dean. Thanks to Michael, Mary never remembered meeting Sam or Dean.
Season 6
Eve transforms into Mary in order to torture Sam and Dean and demonstrate her mother's love for her "children." However, Dean tricks her and poisons her with her only weakness, Phoenix ash and taunts her, saying "call ya later mom." Eve turns back into herself and dies.
Alternative Reality
Mary
In another world created by a Djinn, Sam got to know Mary and grew up with her. Without Mary's death, Sam and Dean never go into hunting. Sam can pursue school without fighting his parents. Sam also comes back for holidays to visit Mary. On her birthday, Sam brings Jessica with him, and announces his engagement to her. Mary is delighted to see this, and is genuinely happy for her son.