>I believe that in case of waifu the "finding each other" feeling is mutual, but what about daughteru?
It's basically the same, except the feelings are different.
>Do you just decide "I'd like this character to be my daughter" or is there some deeper mutual feeling?
I never expected it to turn out like it did, the emotions he brought me lead me to the decision to accept what type of relationship we had formed.
>Do you see them like "children you have with your waifu" or "children you adopted with your waifu" or something else and imagine you all like a family?
Something else entirely, though I would consider him part of the family.
>How did your waifu react to getting a daughteru?
It took a long time to figure out our relationship, and my waifu didn't take it so well at first, so I tried to distance myself from that person since I did not want to go through with anything my waifu was uncertain about. Eventually, my waifu warmed up to the idea of having him around more.
>What if the daughteru's and the waifu's source materials are too different, do you "merge" them somehow in your headcannon or do you "take them out" of their official cannons completely?
His world is different than ours, while my waifu's source takes place in the real world. Obviously, things that are present in his source don't exist in our world, so I merge him into ours and see it as an AU after his story in his source has ended.
>How do you spend time with them?
We like to cause mischief together, which my waifu doesn't really like, so we're trying to learn to behave ourselves. I used to spend time with him and my waifu separately, just doing every day things, but recently we've spent more time together as a family just traveling or general hanging out and stuff.
>If you have more daughterus how did your family grow?
I don't really plan on my family growing. I think it's a miracle in itself that I was able to have such strong feelings and a connection with someone who isn't my waifu. If it happens, I will try to embrace it, but I think I have my hands full as it is.