If you don't like the other idea, maybe some more with Molly, Stan, and forest spirit Angie?
Stan paced in front of the part of the forest the McGuckets lived in. It was sealed off to mortal eyes, but he and Molly had been granted access literally ever since they met Angie. He wasn’t used to not being allowed in. This was his sixth month being stuck on the “mortal” side.
“Come on, you tree- deer- whatever people!” Stan raged. “I haven’t heard from any of you in months! I haven’t seen my girlfriend for half a damn year! Let me in!” He kicked a log.
No, Stan. Kicking the forest they protect won’t help your case. Stan sat down on the log he’d kicked, mumbling an absentminded apology to it.
“I just- I’m worried, okay?” Stan vented to the empty forest. “You all vanished without saying anything.” There was a slight rustle. Stan whipped his head around. Lute had emerged from the enchanted area he lived in, and was watching Stan silently. “Lute?” The forest spirit nodded.
“Do ya want to see her?”
“Duh!” Stan said, jumping up from his seat.
“Then come on.” Lute turned around and began to walk away. Stan bolted after him, relieved when he was able to cross into the McGuckets’ part of the forest. Lute was uncharacteristically silent during their trek. Stan looked around, fascinated by the magical wildlife. Sure, everything in Gravity Falls had magical creatures, but where the McGuckets lived, it was even more intense.
“I, uh, I don’t recognize this part,” Stan said, suddenly realizing that they weren’t headed toward the McGucket homestead. Lute shook his head.
“That’s ‘cause you’ve never been this way. Where I’m takin’ ya, no mortal has ever seen before. It’s sacred territory.”
“You’re not gonna ritualistically sacrifice me or something, are you?” Stan asked, half-joking. Lute eyed him.
“Nah. Time’s passed for that,” Lute said flatly. Stan’s blood ran cold.
“So you would sacrifice me-”
“Shh!” Lute hissed, thankfully cutting Stan off. “Be on yer best behavior in this glen, understand? Yer ‘bout to walk on hallowed ground.” Stan swallowed nervously and nodded. Lute carefully parted a curtain of vines hanging from sassafras trees, revealing a cleared area. A thin coat of spring green grass covered the ground, and there was a fountain bubbling in the center of the clearing. Looking at the water made Stan’s eyes hurt. Someone was sitting on the edge of the fountain, facing away from Stan. Lute nudged Stan forward.
“Angie?” Stan asked cautiously. The person lifted their head, deer ears turning his direction. Slowly, the person stood up and turned to face him. She was hidden through a sheen of the eye-hurting water from the fountain, but Stan still recognized her. “Angie!” Stan strode quickly towards her. “God, it’s too damn long.” Angie nodded. He finally came to a stop in front of her. “You better have a good reason for all this weird stuff going on. And Lute talking about sacrificing me.” He suddenly realized that Angie was cradling a bundle.
“I do,” Angie said softly. She carefully parted the folded blanket wrapping the bundle in her arms. “His name is Emory.” Stan’s heart stopped. He stared at the infant in Angie’s arms. A few wisps of caramel-colored hair covered Emory’s head, not concealing the tiny nubs that would eventually become antlers. His deer-like ears twitched as he clenched and unclenched his fists in his sleep.
“Is- is he… mine?” Stan choked out. Angie made a small smile, still watching Emory.
“I’ve never met anyone else with that nose, darlin’.”
“But you’re- but we- we never, y’know, did it,” Stan said. “‘Cause you’re, like, half deer, and you said a human couldn’t knock boots with a forest spirit like you, anyways.”
“Forest spirits don’t follow the same rules as mortals,” Lute said, abruptly appearing by Stan’s side, startling him. “When two people have a connection, of mutual trust and love and understandin’, a child is created from those feelin’s.” Lute gazed at his nephew. “That’s how all of us were born. From the deep, personal connection Ma ‘n Pa had with each other.”
“Am I supposed to just, I dunno, expect unplanned pregnancies from here on?” Stan asked weakly.
“No. As far as I know, only one offspring can be born from a human-forest spirit union,” Lute said.
“Why didn’t you tell me?” Stan asked.
“There are traditions even I can’t ignore,” Angie said in a low voice. “And the ones regardin’ mortals and forest spirit offspring are included in that category.” Emory shifted in her arms. “He can leave the forest, by the way.”
“Emory, he’s only half forest spirit. He’s free to go wherever he pleases.”
“But you can’t,” Stan said. Angie shook her head.
“No. I can’t.” Angie cleared her throat. “Do ya want to hold him?”
“He’s my kid. Of course I do.” Angie carefully handed Emory over to Stan. She and Lute watched Stan adjust his hold on Emory instinctively.
“Yer good at this,” Lute remarked.
“I learned how to hold babies when Molly was born,” Stan replied. Emory opened his eyes and yawned. Stan’s mouth quirked into a smile. “Damn, he’s cute.”
“Any fawn of my sister’s would be,” Lute said proudly. Angie rolled her eyes.
“That thing you did with your house,” Stan said suddenly, “do you think you could do it again?”
“Convincin’ livin’ trees to braid together ‘n form a dwelling?” Angie asked.
“Sure, we could. But why?”
“Well, you don’t like people chopping down the trees in your forest, but we’re gonna need to make a house,” Stan said, idly rocking Emory. Emory giggled.
“What for?” Lute asked.
“So Molly and I can live with you and Emory,” Stan replied. Angie’s eyes widened. “What, did you think I wouldn’t wanna help raise him? Antlers or not, he’s still my son.” Stan shrugged. “Molly’s been bugging me about moving in with you for a while anyways.”
“Do ya really have to hide yer emotions like that?” Lute asked Stan.
“Yeah, pretty much. Mind showing me the way back? I gotta go brag about my half-deer kid, now.”