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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Missing his sons was something that Gaster had really expected to happen when they would go to leave, but he had absolutely no idea that he would end up missing them this much. He knew that they had gotten to the location safely though, as Muffet had called Grillby to let them know that they had taken Sans, Papyrus and Frisk to their new home that they would likely be living at for awhile. The father was extremely happy that they were safe; it just made him sad knowing he couldn't see them as much anymore. 

"Earth to Gaster." A familiar flame monster joked, as Gaster was currently sat at his bar, just staring into space as he was resting his chin in his hand. Though when he had made that joke, the skeleton snapped out of it and weakly smiled, letting out a brief chuckle as he went to take a sip of his small glass of scotch. Seeing as he didn't really answer, Grillby decided seeing as he wasn't serving anyone at the moment, that he would step out from behind the bar, and he went to sit down on the stool next to him, leaning close to him. "What is the matter? I haven't seen you this glum in awhile. Please talk to me." 

"Grillby, I'm okay, really. I'm just... Missing Sans and Papyrus a little, that's all." Gaster answered with a tiny shrug, lightly swirling around the scotch in his small, flat-bottomed scotch glass. The reason why he was upset couldn't really be fixed, not until he got over what was making him upset all by himself. Sadly smiling, Grillby went to put a hand on top of Gaster's shoulder and gave it a small squeeze, as if to let him know he was there if Gaster did need to talk. They all missed Sans too, and Papyrus, and of course Frisk. It was a shame they weren't all here anymore.

"It isn't like we'll never see them again though, and just think, that it's to keep them safe." Grillby told him, wanting to reassure Gaster in any way he was able. He hated to just sit by and say nothing as it was clear the skeleton was down, so he wanted to be able to try and cheer him up in any way he possibly could. Slowly nodding, Gaster went to take one of his hands to put it on top of Grillby's that was still on top of his shoulder.

"Thank you." Gaster spoke, going to smile towards his boyfriend, as he was filled with gratitude at the flame monster's kind words and his caring attempt at trying to make him feel a little better. His attempt did not go to waste, as while it did not make him feel immensely better, he felt somewhat in a better mood thanks to his words. "But really, do not worry about me. I will be fine eventually once I've grown used to it."

"Don't be pathetic. I'd always worry about you." Grillby teasingly grumbled, giving his shoulder a light playful slap while he went to get out of his seat, as he had to serve some other customers, (despite actually wanting to stay at Gaster's side to chat to him). But unfortunately at the moment, he still had a bar to run. But he would never forget about the skeleton man, who he gave kind glances towards every now and then to try and make his day better.

Back in the house where the trio were living, Frisk, Sans and Papyrus were discussing what they could possibly do for jobs in the living room, sitting on the couches together. This was the day after Papyrus had gone out searching for something, to not much success (it was also the day after Sans and Frisk had allowed themselves to soul bond, and without a doubt the both of them were still thinking about it with extreme amounts of joy). Though, while looking around, Papyrus mentioned how he had seen something that Frisk might want to do, as there had been an ad in a window.

"And what is that?" Frisk wondered, only to get the answer of Papyrus wondering if she ever thought about being a waitress. And truthfully, since coming here, she had honestly considered such a thing. Just because it might have been a job that wouldn't be too difficult to obtain, and she might be able to meet some new people who she would be able to work with. Sans rose an eyebrow at the thought of Frisk being a waitress. 

"a waitress, huh? where some random guys could probably ogle over ya, just 'cause ya would be in some kinda uniform?" Sans asked, but then he rose his eyebrows a little, actually starting to wonder what Frisk would look like in a waitress uniform, and before he knew it he began to blush up a storm, and that's where he decided to try and stop his imagination. He didn't want to allow his mind to go down to some kind of rabbit hole, when thinking about the combination of his girlfriend and a maid's outfit. 

"Guys wouldn't ogle me... Well, even if anyone tried, I'll just let them though I'm taken by a skeleton who easily gets jealous." Frisk poked her boyfriend with a tease, who lightly grumbled in return. "And besides, I can already tell, you're thinking about how I would look in the uniform, aren't you?" She found it impossible not to giggle when she had caught her boyfriend red handed, considering his whole skull started to go bright blue, while he covered his face with his hands.

"ugh... don't tease me." Sans quietly complained, while both Frisk and Papyrus cracked up into laughter at his reaction. From him being so adorable, Frisk lightly kissed him on the skull and told him she was only joking, as his cute reactions were always so worth it. Sighing, Sans smiled and lightly nuzzled his skull against Frisk's lips when she kissed him on the skull. Well, while she appeared to think he was cute to her, she was really cute to him too. 

The issue was though that he wouldn't be the only one who would find her adorable. Others would likely fuss over her, and maybe even come along just for the sake of seeing some attractive girl in a uniform. He hated the thought of other guys trying to flirt with her, (even if he trusted Frisk not to flirt in return), he found it difficult not to feel a bloom of jealousy at such a thought. But it's not like he could stop her from getting the job if that was what she wanted, he didn't want to be controlling of her because that would just be unhealthy and horrid, wouldn't it? She could make her own decisions; she could do what she wanted to do, because he believed in her, knowing she was one of the most amazing people in the world who he had been fortunate enough to meet.

Now it was just thinking what he and Papyrus would do, though he was sure his little brother likely had it more figured out than he did, and even if he didn't, he was sure the taller skeleton would find himself a good job. Papyrus was a great cook, Sans thought, so perhaps he could always try to become a chef or something. Such a job was likely suitable for him. "why don't ya try to become a chef or somethin' paps. ask the place that frisk is goin' to if they want any new people to try and cook or somethin'." Sans decided to suggest, seeing Papyrus' face light up.

"OH! THAT'S ACTUALLY A GREAT IDEA! THANK YOU, SANS, I'LL DO THAT!" Papyrus beamed widely, grateful to his older brother for being thoughtful and making such a suggestion, while Sans shrugged as if it was nothing. He was glad to be able to make Papyrus happy and if it was to help him get a job he was also happy for that too. What he was going to do himself, he had no clue whatsoever. But he would just have to look around and try to find something for himself. A normal job... One that he hadn't been doing since he was 17.

He would have to try and fit into actual normal society.