HermAlva/HalVa headcanons because they're plaguing my mind (sorry it's long, like, it's their entire before manor lore):
Alva was the shy one
Herman was the first to confront Alva; they were both researching the same thing and Herman was like, "hmmm, he's cute, let's talk to him."
They became friends and there was always mutual feelings but none acted upon them
Herman met Maria(Luca's mum) and Alva watched sadly as Herman started his own life with Maria. He was never the less there for him tho
He met Luca before, when he was born to be precise. I don't care what NetEase says, it's my turn making the lore
Herman and Alva started the invention but suspicion started arising since they spent so much time together, alone, so Alva found a woman to marry who was in the same predicament
Alva and his wife made the mutual agreement they could see others in secret since they weren't in love but simply married for the social status
Herman took Luca with him to the lab sometimes
Herman cheated on Maria with Alva
Alva wanted to stop it, but he adored Herman too much
When Maria died Herman was heartbroken, of course, he did love her, but he stuck with Alva
Herman decided to say f you to society and chase a relationship with Alva
Alva was hesitant but agreed if they stayed together in secret
Luca grew up with the two of them taking care of him
Herman and Alva were pretty much Luca's dads
Herman kept trying to persuade Alva to run away with him and Luca but Alva declined, not wanting to throw everything they made together away
After an argument Herman took Luca and left, saying they just needed space
Alva was heartbroken and tried to do his best to get Herman to come back, or at least make sure he's living happily
Miscommunications happened and they lost contact, leaving Alva alone and heartbroken, with not even a proper wife to go back to
years later Luca came to his lab and asked to be his apprentice, claiming to have heard all about him from his father and having his biggest wish to work with him
Alva gladly accepted and Luca was surprised with the acceptance
Alva soon realized he didn't have memories of the two from when Alva helped raise him
Alva didn't stop treating him as his own son though
Eventually Alva tells Luca about their past and more misunderstandings happen
Alva protected Luca and died doing it