My husband fathered a child a year after we married

Note: I am not a parent but I think it could work to get the whole thing out in the open. No 'secret' daughter. She's your kids' half-sister. Call her your stepdaughter if you like. It's not a perfect term but it's close enough for horseshoes and hand grenades.

I would openly socialize with everyone and encourage the kids to meet and break bread with everyone. Their father did something and made mistakes. He (I assume) feels terrible that he wasn't there for his third (technically first?) child. But he can be there for her now, just like he can be for the kids he has with you. And you can be there for her, too. You don't have to financially support her unless your husband wants to, and you'll never be her mother. But you can be her friend.

Thank you for your reply and advice. Unfortunately my husband's daughter has only met with him on 3 occasions and doesn't want to meet me. I did contact her by text but received no reply. Our 2 children don't even want to talk about it. I think my in-laws should know about their grand daughter but my husband won't tell them. I think my family would freak out if they found it. I feel as if my whole life is a lie.

jespah has given you great advice.

Talk about her in general conversation - so her existence starts to be more natural to everyone. Text her again - invite her over for a coffee on an afternoon.

Let your husband and children know that you are not going to ignore the fact that you have a stepdaughter, that your husband has three children, that your daughters have a half-sister. Don't make this a 'do you mind if I do this' situation. Just do it.

No secret child. Don't think about it that way. Don't use language like that.

___

My best friend's family has a similar situation. Her oldest brother in law found out about his daughter when she was in her 20's. It was awkward for a bit but she has now been absorbed into the family. She spends time with her cousins/aunts/uncles and was lucky enough to know her paternal grandparents before her grandfather died and grandmother's Alzheimer's became severe. Her stepmother absolutely adores her.

Not all situations work out as wonderfully as this one has but it really only takes a couple of consistently supportive family members to make it work.

it does seem that you are going to have to do some work with your daughters - teach them , by example, how to be gracious and accepting

Thank you all for your advice. I realise it is going to be very difficult in the future. My husband is not sure that his daughter wants to become a major part in his life. I promised that I would not contact her again if she didn't respond as I didn't want to harass her. Whilst l am still trying to forgive my husband it was wrong that he betrayed me and I am finding this very hard, even 3 years after finding out. I think about his daughter every single day and how hard it must have been for her losing her mother and not knowing the love of a father. I just wish her mother had had the decency to let him know that he was her father when she was born. I am a Christian and know that this should not have happened. My husband has paid nothing towards his daughter for all of her 24 years, not financially nor his time. She is now a young mother herself and I feel so sad about the whole situation. I can't bring myself to leave as I know most other wives would have. My daughter will not want to meet her half sister and she is a very kind girl, but when she found out she told her dad that she would hate him until the day he died. They have since started speaking but she will never have the same respect for him. My son is a very quiet and anxious young man and never wants to speak about her again.