Sans is a MONSTER and not a HUMAN, so he doesn't follow HUMAN biology like a HUMAN skeleton. Same with Gaster and Papyrus.  

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"Ugh, I'm sooo exhausted!" Blair let out a huge yawn, as she decided to flop onto the living room couch, laying her head lightly upon her boyfriend's lap. She opened her two dazzling blue eyes, only to softly smile when she saw Andrew beaming down at her, asking if her day had been fun. She gave a small nod, as she stretched her arms up above her head a little. "Yeah... Frisk managed to find the dress that she wanted, so she was super happy..." Blair said. It was funny how she and Frisk first met, and how much they hated each other... Because now, the fox could gladly be happy for the human girl. Really, it was funny how a lot of things had turned out. 

She used to be part of that shitty group, the group that sometimes still haunted her nightmares, even to this day. Because of... What they did to her. When she had been part of that stupid group, and she had been taken away from all of her friends, from Sans, who was her boyfriend at the time... Her whole world had felt like it was ending, like it was falling apart piece by piece. She had given up on the idea of a hopeful future, and became more used to playing the villain. A fox with a mask was all she had become at that point. A monster who liked to cause nothing but hurt, who seemed like she was having a blast when doing it, but inside: she was screaming.

It had been a genuine shock to see Sans again, the day they had managed to capture him. But instead of trying to rescue him, instead of doing what she wanted internally, she just tried to hurt him; go against his wishes, his comfort. When thinking back to it, she felt so awful, because she could never forget how uncomfortable he looked, how disgusted he looked, especially being someone who had terrible things done to her, against her own choice. 

Then she was locked up, and she met Andrew. She had no idea that the boy she was going to try and use to escape, would end up being the same person who she would end up in a relationship with, or that she would even remain with him for as long as she had. They even lived together - that was insane to her. 

Life really was funny sometimes. True, her haunting past did sometimes make having a relationship extremely difficult, for obvious reasons. Even years later, sometimes it was still difficult not to just want her personal space at certain moments, but it made her glad that she had a human who was extremely patient and understanding. People like Andrew or Frisk who put up with haunted monsters like her and Sans were way too good for this chaotic world. They really were.

"That's good... It's still weird to think that it won't be that long until they'll be married." Andrew murmured thoughtfully, lightly playing with a couple of strands of Blair's hair, as he stared down towards her, with her still smiling up towards him. Him and Sans had never been on the greatest of terms, and even if it wasn't like Andrew had known him since forever and ever, for some reason the skeleton just hadn't struck Andrew as someone who would want to get married. Maybe it had just been his seemingly negative attitude, that had made the human assume incorrectly. Though, it had definitely been made all the more clear, the more he saw Sans and Frisk spend time together, just how much the guy clearly cared for his fiancee. Even if they had had a couple of bumps in their relationship, they obviously dearly loved each other; Sans dearly loved her.

Andrew was glad. He would have felt guilty being happy himself with how things currently were, if Frisk wasn't happy. 

"That's what I said." Blair grinned. "I'm sure it will be a nice wedding..." It would also make her glad to see her own ex happy in life. There was no point in being bitter, or wishing if things could have turned out differently. Don't get her wrong, at one point, being with that skeleton had been her ideal future, before everything had gone horribly wrong. But now? She was just glad that her life was back on the right track, and so was Sans'. It was her fault that he had turned out to be such a hostile, distrustful, paranoid monster, so it just wouldn't have made sense for them to end up together again. They had to go their separate ways, and Blair had accepted that a long time ago, while being with Andrew. 

"Agreed, and I'm really happy for them." Andrew spoke truthfully. Yeah, him and Frisk had been together at one point, for not very long, and that was just natures way of telling them that they weren't compatible for one another, that they were much better off being friends. It had sucked at first, it had hurt a lot, and was hard to see Frisk being happy with someone else, especially the person who just hated him with a burning passion. But with time, and with falling for Blair, he was able to move on and accept it. It felt a lot better to be glad for them, than to be sorrowful and regretful. 

"Me too."

"And I'm glad that I ended up with you." Andrew decided to speak up, seeing the look of genuine surprise cross the fox's face, until she seemed to look embarrassed, as her blue eyes trailed elsewhere. What was with him suddenly saying something like that? Was it any surprise that she now flustered? Andrew chuckled. "I mean it."

"Why have you got to say something like that for, for no reason?" Blair pouted. 

What the human said was true though. Despite growing up in a family who was extremely different to himself, who would rather hurt people, mainly monsters, because they had an extreme distaste towards them, Andrew had never had a problem with monsters. In fact, he had been someone who found them more cool, and was more fascinated by monsters, rather than hateful towards them. It was why he had been so surprised when he met Frisk, and she claimed to have monster friends. Being invited into Frisk's life, was like being a part of a whole new world he never would have gotten to experience if he had just stuck with his hateful family. He never would have met Blair. 

Did Andrew miss his family? Not really. At first, maybe, maybe he had. It had felt strange to be separated from them, scary actually. Especially when he thought he was going to die, as he thought that skeleton was going to kill him. But then there was kind monsters like Toriel, who had treated the wounds that Sans had dealt to him when he had been his hostage. It really made him see, (more than he already did), just how wrong his family were, and how he would likely never, ever fit in with them. What were they doing now, his family? He had absolutely no idea. As far as he knew, his parents; his brother... They were all dead. They had likely died during one of Sans and Frisk's missions, or something... 

But maybe that was their fault for being on the wrong side. They could have lived happier, and longer lives, had they just not wanted to keep hurting innocent people who never did anything wrong. Their group had no right to take away Sans' and Papyrus' father from them, when they had kidnapped him, and they had no right to hurt anyone who tried to rescue him. As far as Andrew was concerned, his family had just been bad people, and he was glad not to be involved with them anymore. At first, being stuck with the Mafia had been frightening, but then it made him realise that perhaps it was what was best for him. Just like how it had been best for Frisk, or literally anyone else who had been part of the group for as long as they could remember. 

"Because I care a lot about you." Andrew admitted. "I know your past has been hard for you, and I know sometimes it continues to haunt you... But no matter what, I'm here for you." Andrew beamed. Sometimes, even he didn't understand how he managed to become a more caring, understanding person, when he had grown up with a family that had such a negative view towards the world. But maybe some things were just never to be understood, and such things were best left unanswered, because you didn't always have an answer for everything. 

Blair smiled. "I love you." She said, knowing she truly meant it. She never wanted to have the possibility of a happy future taken away from her ever again. Being with this human made her truly glad she was still alive, despite her terrible past, and she always wanted it to remain that way. It made her glad that Andrew seemed to feel the same way in return, as he gently spoke in return, putting a hand to her cheek. 

"I love you too."