Some things I've learned from reuniting with my son:
1. This is not your child. This is another adult. You will want to treat this adult like your child, and you will be tempted to treat this adult like a small child. You will be wrong. You need to ramp back on those maternal feelings and do your best to get to know this adult person on their own terms This will suck a good half of the time. (Completely fucked this one in the ass with an Almaden bottle. Massive fail.)
2. This is not a member of your family. This is a person who was raised in a completely different family culture than yours. Your way of relating as a family member will not mean a thing to this person. Their way of relating to you as a family member will seem strange and off-putting to you. You'll have the feeling that you have to 'break them in' correctly. They already are broken in. You are a guest in this home; you're the one who needs to learn how to play by new rules. ( I absolutely failed this one. Spectacularly. Well no, wait, I did pretty well over at his place for the most part. Just not so much with him personally. At all.)
3. If this person has close family, you will feel jealous. Grit your teeth and do the right thing and stand aside and let them have this relationship. (This is one of the few things I got right on the first try, but I think it's just because I'm not a terribly jealous person to begin with.)
4. If this person had a shitty upbringing, you need to tread very carefully, PARTICULARLY IF THEY HAVEN'T ADDRESSED THE ISSUE YET. Abused kids grow up into hurt adults, but they still have a horrible longing for the love, approval and caring of the parents who raised them. Not you. Any good relationship you form with this person is going to make them feel very guilty. Anything negative you might venture about their family of origin will be met with denial, defensiveness, and shame. DON'T GO THERE. ( I fucked up this entire part like a big dog.)
It's probably a real good idea to avoid meeting the abusive parents. (Another thing I got right. Go me!)
5. There will be a period of time after the initial 'wow' wears off when you start knocking the corners off each other in the process of learning to live in each others' life. (This is where we're at now. I used a 20 lb. sledgehammer. Don't use a 20 lb. sledgehammer. I stand a very good chance of never seeing my kid again.) It's like that first year of marriage...all the new rubs thin and now you're down to the icky, goofy nuts and bolts. You forget to flush the toilet, and they let the dog stand in the dishwasher and eat the crud off the bottom. You will argue and disagree. It will suck. Family will take sides. There will be robots and kung fu and someone will leave a flaming bag of dog crap in your car, and it will be retarded.
6. Sometimes there are things that simply will not work. This person may be too different for you to have an ongoing relationship with. Remember, this person is a stranger. Not all strangers turn into friends. Nature doesn't mean that much in the long run. You should probably just let it die a natural death and try to leave on an up note. All you'll get out of it is knowing how the story ended. And sometimes that's all you get. (My boy, turns out, is a shit kickin', country-western singin' he-man conservative redneck. I am a funk-soul armed liberal bisexual feminist hippie biker. The twain are not meeting well. AT ALL.)
7. Sometimes, you will not understand their family. Be gracious and for the love of God keep your negative opinions to yourself. (Shaky on this one....but I've done pretty well on the main. Right up until lately.)
8. Your family, meanwhile, will be very jealous and protective...angry at the interloper and angry at you for letting them in. They will cause all kinds of problems for themselves and for you. You will need to spend a lot of time reassuring them. (The way this finally shook out for me is that my daughter and son haaaaaaaaaaaate each other, and my husband has backed way off because me and the kid's thing is just too fraught. It's....how you say...in a state of flux.)
9. I have no advice to people who neglected to mention their youthful indiscretion and then had their grown indiscretion come knocking at their door. This didn't happen with me. Me and the biker have at least two 'indiscretions' between us and all was known from the get-go. It was the 70's, OK?
10. You may experience a terrifying rush of oxytocin and 'fall in love' with your child. This is not 'romantic' love. You aren't a pervert. (Nailed this one! God I hope it never happens again. I thought I was the biggest freak in the entire world.)
11. I also have no advice to give about differences in religion. That wasn't an issue. Can I get an 'amen'?!! I'd imagine it sucks pretty bad the more fundamentalist people are regarding their beliefs. Same goes for politics. ( I actually got this one right. I've openly scoffed a few times when Nixon, Reagan or either Bush appeared on the TV, but I've never got into any kind of political discussion with the guy. Mainly because I'm not too politically knowledgeable, and why sound like an ignoramus.)
12. Keep your opinions to yourself in the beginning. Instead focus on finding out what theirs are first. (I just took a big old runny shit all over this one. Can't keep my big mouth shut, never had an opinion I didn't feel obligated to beat other folks over the head with. Just yap yap yap yap yap yap. It wasn't pretty.)