To be annoyed at close family for not saying anything...

[notapartypooper]

I don't want to go into too much detail, but a family member (we didn't know she existed until recently, as her mother didn't divulge she was a relations child).

She was welcomed into our family by everyone but as much as I have tried I just do not like her, she has caused lots of issues for my dad, who is not in the best of health, always borrowing money which she never pays back. I challenged her about and told her it needed to stop, she had no idea that my dad had told me and got very defensive. At family gatherings I now avoid her rather than rise to her bait.

She has a young ds and has arranged a party for him and has invited all the young children in the family... except mine. They have been at a cousins house today so now know they aren't invited and are uspet.

Of course she can invite who she likes, but I can't help but feel that by going to the party my siblings and my df are condoning her spiteful behaviour. I am also upset that not one of them have challenged her about excluding my dc.

That would upset me too. Do they know about the conversation you had with her about borrowing from your dad? Did they know you weren't invited? It sounds like a difficult situation all round. They might feel differently about her and still want to include her. In which case they might just not want to get involved in your dislike of each other. If that's the case then I would maybe tell them that you are hurt by it, but otherwise try not to dwell on it too much, and definitely try not to fall out with them over it. Tell your children it's not so bad and that there will be other parties and events to go to. It must be really frustrating for you that she is treating your dad badly, but short of advising him, there's not a lot you can do about decisions he makes about own money. I would carry on doing what you're doing and try to keep a distance.

I wouldn't know who the guest list is for someones party - do your sibling know who has and hasn't been invited?

Borrowing money from your father. Is she another daughter? are you jealous of her arrival? Because it's none of your business who your father lends money to, unless he's in his dotage and being financially compromised. It's up to him to get the debts repaid, not for you to wade in and stir it up because, in your own words, you don't like her. Which brings me roundly back to the party. You don't like her, so why would you want to be invited? You can't have it both ways.

DarlingGrace
I would point out that it's her kids (who haven't done anything) that haven't been invited. In situations like this I think kids should be left well out of it, and it is spiteful behaviour.

Why not ask another sibling to ask her if they can bring your kids along as they're very upset at being left out? Your other siblings may not have known you weren't invited, but by taking a half moral high ground by asking if the kids can go but staying away yourself it may stop stop the situation escalating further?
It's very difficult to give advice without knowing exactly what's been said etc. I know from experience what it's like to have a sister who is emotionally manipulative (now everyone realises, they generally do trip up in the end) and mine has been around for longer than me :p

Why would she invite you and your children when you go out of your way to avoid her at family parties?

I can't say I'd invite someone to my child's party who I'd had an unresolved disagreement with and who actively avoids me. That's not spiteful, it's normal not to invite people you don't get on with to your party's.

It's very unfair of you to expect your siblings and DF to snub her party just because you can't handle the fact that people you are horrible to tend not to invite you or your children to parties. Why on earth should the rest of the children miss out because you interfered in what your dad does with his own money?

Sorry, buy you are very much the unreasonable one here.