Father to Grace, Lucifer took Grace from where she had 'died' and helped her return to the land of the living her true self. Nephilim. It was painful for Grace as it had been her best friend who killed her at the demand of Ruby and she was determined to make Sam pay for it, even though her father told her not too. Although he was Lucifer, Grace adored having a father who cared deeply for her, enough to care for her during a difficult time. Travelling to the future, Grace was devasted to see how she turned out when she stood by her father rather than Dean, Castiel, Chuck, etc. She was heartbroken when her uncle was killed by her father, Grace cut off any contact with everyone until Castiel appeared to her and comforted her as she grieved for her uncle. When Lucifer killed Castiel and Bobby, Grace begged him to stop and he told her it was destiny for him and Michael.
Gabriel had watched over Grace from the moment he had heard of the possibility of Lucifer's child. One night when Grace was months old, Gabriel saved her from a demon attack. Nicknaming her 'Gracie-Boo', he continued to watch over her for the next six years. Even appearing to her one day after her sister had pushing her to the ground after throwing a tantrum. Helping her up, Gabriel gave her a locket with an angel on it, saying it would protect her from the others and demons before placing it on and telling her to hide it. The next time Gabriel appeared to Grace, she was 18 and was in a car that her sister was about to crash. He appeared through the barrier protecting her from the angels and demons and grabbed her moments before the car struck the wall. He stayed with her unconsciencious body until the ambulance arrived at the scene and then disappeared once more for a few years. When Gabriel saw Grace again, she was hunting with the Winchesters. Thinking he was a Trickster, they tried to stop him but after Dean and Sam had thought they had killed the Trickster, Grace returned to grab her necklace which had come off in the hall and saw Gabriel. When Dean called to ask if she was coming, Grace hesistated before calling she would be right there. Before leaving as Gabriel watched after her curious about why she hadn't told them the truth. When she met him again, months later, Grace is annoyed that he keeps killing Dean as opposed to Sam's devastation. He agrees to stop as Grace asks him too and says in future, he will tell her why.
Nearly two years later, Grace, the Winchesters and Castiel have to deal with alternate versions of tv shows. Gabriel insists that Sam and Dean have to fulfill their destinies as Lucifer and Michael's true vessels. But they trap the Trickster in a burning ring of Holy Oil, Gabriel reveals himself and asks Grace why she never gave him up the first time, it was the bond they had from her childhood. Grace gets angry at Gabriel and flies off. Grace secretly returns and sets Gabriel free after the guys had left. She asks him why wouldn't he just have told her straight off and Gabriel explains that not even Lucifer knows he was protecting Grace from the other angels, especially Michael and Raphael. That if he had told her the truth, she wouldn't have been able to handle it. Grace admits he was probably right and that she, like him, wants the fighting to stop. Gabriel comforts her as she realises if it comes to a head, she will have to chose between her father and humanity, which Gabriel tells her is the best part of her before disappearing.
In Muncie, Indiana, at The Elysian Fields Hotel, Grace feels the presence of power almost as strong as her father. When she tries to explain to Sam and Dean, they don't believe her before she disappears from the room they are staying in. Next time, they see her, Grace is by Baldur's side and impatiently trying to tell them not to harm the brothers before Gabriel turns up. He is a little surprised to see Grace by Baldur but plays on it. He sends Grace and the boys back to their room. When he turns up in the room later, Grace goes to choke him before Sam stops her. When Lucifer turns up, Grace refuses to leave Gabriel and listens to everything he says before saying he was trying to keep Grace sane and protected because if Lucifer took over the world and forced her to join him, it would end her. And that he was more of a father to Grace than Lucifer or he would have put her first before Lucifer killed him. Screaming, Grace woke up in the Impala before going into a state where no one could reach her, until the boys called Castiel.
Grace first met Castiel when he appeared to Dean during the night he was sent back in time. Castiel thought it important for Grace to accompany Dean and returned her too. After that, Grace was often amused by Castiel's appearance, especially when Sam gushed over Castiel, Uriel and angels in general existing. He is also the one to reveal to Grace that she is a Nephilim, technically an Angel since both her birth parents were Angels and their hosts were human. When Grace returned from her death, Castiel was curious to know how she woke up completely sane. Grace explains that her father sat with her until the insanity had subsided and let her go her on way. She also felt the connection with Castiel before she died and earned her own wings. She was transported to the future with Dean and was drawn to Castiel's new view on life and felt the Angels had abandoned Earth. When discussing what happened to her, Castiel kissed Grace to stop her asking too much and they slept together before going with the Deans' resistance to against Lucifer. She was knocked unconscience by one of the resistance members against Castiel's wishes and woke up to see Lucifer kill future Dean and future her stab Castiel with an Angelic Sword, as he watched the present version of herself with a smile on his face. Heartbroken, Lucifer tried to comfort his daughter but she refused as he was in Sam's body and although angry at Sam for killing her, she was angrier at her father for having her watch Castiel die and standsby Dean. When they are transported back, Dean and Grace are about to face off with Zachary when Castiel transports them to him and Grace embraces him, as Dean tells him not to change. Grace remains with Castiel as Dean goes to see Sam. The next time Grace sees Castiel, it is when the Trickster is revealed to be her uncle and an Archangel; Gabriel. When Castiel is weakened from the banishing spell he performed, Grace is in a numb state after Gabriel's death, they have to help the brothers when Pestilence arrives. Grace snaps out of her numbness to help Dean and at the end of the episode, is comforted by Castiel as she finally cries over Gabriel's death at the hands of her father. The last straw in her relationship with her father was when he killed Castiel and Bobby, she finally snaps. But after the fight, she hugs Dean as Castiel appears. After he brings back Bobby, Grace jumps into his arms and kisses him before hugging him which surprises Castiel.
Ever since she was a child, Grace had had a huge crush on Dean. Which came to a head one night when Dean did try it on with her after a hunt. Realising that it was their friendship she valued, Grace refused. But one night, months later, Grace and Dean did sleep together after she thought he would die. But after that, Dean and Grace reverted to friends.
Since childhood, Grace and Sam bonded over their mutual dislike for their siblings, even though they adored them. When Grace found out that Lucifer was her father, Sam was the one she confided in. She also knew that when Lucifer took over Sam, she could say what she wanted as he would looklike Sam and that didn't scare her.