My ex wife and I divorced 10 years ago. For the last 10 years I have had joint custody of my 14 year old son. 6 months ago her boyfriend dumped her and kicked her out, leaving her homeless, and I had to find out through a third party that my son was actually living at his aunts house.
When I confronted my ex wife about this, insisting that if he had one stable parent, he should live with that parent, not an aunt, she said that she would be getting her stuff together soon.
6 weeks later she emailed me saying she had just done a DNA test and that my son was actually fathered by her co-worker from 15 years ago. Apparently she had tracked down the "father" and asked him to do one of those $99 home paternity test kits. A few days later I got a copy of the paperwork in the mail.
I was crushed. I called in sick for I don't know how long, and then drank myself stupid for about a week, while thinking some of the craziest, most angry, spiteful, retaliatory bullshit a guy could conceive of.
After about a week of this I managed to pick myself up, dust myself off, and call my son to tell him that I may not be his "father" but I'm still his "dad" goddammit. I told him that no piece of paper is ever going to change that. I told him that he is everything that he is because of how I raised him. I said that I would always love him.
You know what he said?
"Good, because I was worried that you'd leave me when you got the news."