Secrets

This sounds a really good option. I'd not mention it to your Dad because he possibly does not know and he could have a heart attack from the shock. No point in telling your own DC. I understand you have a nerd to know the rest of your family not so much.

I wouldn't hurt him. Whatbis to be gained by sharing that bombshell. He is your dad end of

I think the @VampireWeekday 's idea of mentioning to your DF that you are thinking of doing a DNA test for fun is a good idea. You might be surprised with what he comes out with. If he doesn't react then you don't have to mention it again unless you want to. Personally I wouldn't. Was your mum close to your aunt's? If she was then I might consider talking to one of them.

What led you to taking a DNA test?

I think your Dad has a right to know

When you say DNA test, did you also do your dad's at the same time? I'm asking because I've read of cases where the child was adopted and the dad knew, rather than an affair, and even cases where the dad was adopted without knowing it but the child assumed that their own mum had been unfaithful, since their DNA didn't match up with their paternal grandparents'.

So I would say to really really think through the options. Perhaps worth mentioning to your dad that you want to take a DNA test and see what he says? He might surprise you with what he already knows.

Gosh your father might not even know! I don’t think you can break it to him at his age it could literally kill him.

He would have no chance of answers either and it would change how he looks back at his life, wife and marriage

You might dislike secrets but this was one kept in order to promote your overall welfare and it seems it has been successful

I would not tell your father

I think you should investigate further without invoking any family at this stage.

There are implications of inherited illness/diseases and the very tiny possibility that you have siblings who's offspring could possibly meet your own children in a romantic setting.

As I said, you really need to take a considerable amount of time before you speak to anyone besides a partner or therapist about this, and you need to carefully consider all of the possibilities before you decide to do anything. Your mother could have had an affair, or she could have been the victim of a crime. Your father may know the exact situation or he may know nothing. This could have been a secret held between your mum and dad with them thinking this was the best way forward to protect you somehow. There are so many possibilities.

The only thing I do know is that nothing can change or erase the fact that your dad is your dad and you are his daughter. DNA is absolutely not the be all, end all.

Is Donor sperm a possibility? It wasn't talked about much then, if they were married for 5 years before you were born it's a strong possibility

Are you certain your mother us your biological mother? Could you have been adopted and they never told you, never realising how easy it would be to find out? Do your siblings have the same parents do you know?

Whatever you do remember your father is the man who loved you, cared for and raised you, the one who you say adores your kids and theirs.

Just don't rush into anything. Do a bit of processing first. Talk to a professional. No need to tell dad or dd's.

Consider that your birth father may be dead, not interested, unaware, horrible, or worse. What if your Mum didn't consent? What if you have half siblings? What if they are dreadful?

Find and speak to someone qualified to help. Experience within my own family was not plain sailing. It is a lot. Sorry you have had this shock and wishing you well OP.

Could there be fertility problems that may not have been discussed back in the day and ‘fixed’ themselves. Do you know if your DB is biologically related to your DF?

If you join the Ancestry pages on Facebook, you will be able to request a search angel. Using your DNA results, they will help you find out who your father is without you having to involve your family. They don’t charge to help.

I'd keep it to myself for now, this is a lot to come to terms with and the reason behind it may be painful.

The issue is that longer term this will come out, DNA tests are taken for fun now often with little thought of the potential consequences.

Could your mother have been pregnant when your parents got together?

I am unsure if to tell my DF as he is in his 80's and I am concerned how he would take this news

I absolutely would not tell him given his age. It's possible that he already knows and made the choice to take you on as his child. Are you the eldest?

I just don't see the point in telling him when all it would potentially do is cause him enormous heartbreak.

Please don’t tell your dad, there’s nothing to be gained.

I'm so sorry, op. Something very similar happened in my family and it caused a massive amount of issues, as you can imagine. I highly suggest you take a very significant amount of time to process how you are feeling, because your emotions will fluctuate wildly as you learn to accept the truth. I would keep this between you and your partner for now until you can think more clearly.