Should I tell them they have a half sister?

More details would help? How old are said children?

So by telling them you will be able to get him removed from his church in shame, which will shame his children and cause them grief as well.

What are you hoping to achieve from this?

Are you seeking a warm welcome or revenge?

He is not worthy of your love or attention because of his rejection of you. Your best revenge would be to find and embrace those who love you.
You deserve better don’t you?

There seems to be more to this question than what is stated. With the information given I would say yes you should contact your siblings and let them come to know you if that is your true desire. Whether your father acknowledges you or not, you should let him know what your plans are so that he might prepare for any derogatory outcome.

Yes. Blood is thicker than religion, water and rejection.

Just be prepared for their negative reception.

You need to think through why you are contacting them with this information. You need to be sure that you want to meet your siblings not that you want revenge on your father.

Since Mormons are big on genealogy, perhaps the contact should come to the siblings not in the form of a statement, but the question, “Are you related to me?” You will either get a “Yes, we are!” or a “Don’t think so.”

When your birth father dies, if you are not mentioned in the will, and they do not contact you, then you have standing to contest the will as a pretermitted heir. That would be the time to make contact.

Are his other children legal adults?
Are they financially dependent on him?
Are they also involved in their father’s chosen faith?
Is your father presently married to someone who knows nothing about you?

If the kids are young and want to be involved with you, the rest of their lives might get complicated to where they’ll have a lot of pressure and not be able to cope well. What’s that saying, beware the best intentions? Look at who’s got the most to loose and weight it against what you hope to gain. Do you want to put your emotions out there for it?

Do you have a desire to know them, or do you feel like contacting them out of anger? If it’s the former, because they’re all adults, I say go for it. But if you want to contact them out of anger, or just to get back at your father, I don’t suggest contacting them.

It depends on what you are trying to accomplish. Give some thought to the possible positive and negative outcomes, and choose which one will be the most benefit to you.

My first thought was to carry on with your secret for the next forty years.

An afterthought just occured to me. you have a right to your own identity. you have a right to know your brothers and sisters. you have dealt with this problem for too many years now and its time to meet your father and your family. as far as his church goes, let the chips fall where they may. i say go for it.

My best friend is 39. She’s Mormon. Her father left her mother and remarried. She now has half siblings. There were no problems with the church. In fact, the church embraces all of them.

Were you a product of an affair? The church is more forgiving than you may think. It sounds like he’s using the church as an excuse. Shame on him.