What can I do now that I've learnt that in 16 years of marraige my wife has always had a boyfriend?

Polyamoury can work, but it's really tough, and all parties have to consent to specific rules. If you pursue this, her boyfriend should be secondary to you.
If it makes you uncomfortable and she doesn't want to do anything about it, leave. You don't necessarily have to get a formal divorce, but a separation could suffice. Start dating again, and find someone else to make you happy. She hasn't exactly shown her commitment to you, which is hurtful. She should accept whatever terms you may or may not have.

Get a DIVORCE right away! She will never stop.

Depends what you mean by "boyfriend". If you just mean a close, male friend in whom she confides, that can be great! Just as men can have close female friends, so can woman have close male friends. But if you mean to imply that she has been having SEX with this man for all these years, there really is no question. She has clearly never taken her commitment to you seriously, and has been deceiving you in the worst way for your entire married life... dump her, man! If this was a fling, or just a recent affair, I would say try to seek counseling and work things out, try to save the marriage. But if she's been ******* around for the entire 16 years of your married life, there's nothing to save!!

Get rid of her. A marriage is a entity in its own right where both parties involved work towards the betterment of the entity. If one is focused away form that...the marriage is broken. Divorce her and find someone who will honour commitments.

There are financial and legal ramifications to getting a divorce after that many years. Analyze the financial result of a divorce in your state: her income, your income, what you own together. The best scenario is if she leaves for the boy friend and leaves you the children. In that way you can organize the divorce a little more on your terms, otherwise she will clean you out and the boyfriend de jour will be living in your house and enjoying some of the alimony. You should not leave your own home. Whatever you do never let her have access to anymore personal information, assets. Quarentine her from your financial situation and file married but seperate until the divorce is finalized. Dude youf family got screwed over. Good Luck. The boyfriend will be spending your kids college money. Good Grief.

**** her get a girlfriend and let her find out so she can see how it feels but try to avoid divorce it would really suck for the kids

Why don't you invite the other guy to have a ********* with the wife. Show her that you are strong and not emotionally hurt with such activity. You must be confident with yourself and go with it. Looking at this it didn't seem to have hurt the marriage. The only thing in questions whether or not you can hand such an affair. Look internally and get your answer.

She is still with you, which must mean something, you don't say how active your sex life with your wife is.
If you are satisfied maybe you can work an arrangement, if she only/mainly has sex with the boyfriend it is time to move on before you get any older.

Get DNA tests on the kids looks or not then decide to leave or sit her down and tell her she wants sex on the side you do to if that is not acceptable to her it is back to the leave option