I can't believe how many people are saying that it's your day, do what you look and your mum will just have to deal with it.
I got married when I was pregnant with my first and we didn't want and couldn't afford a big wedding.
My sister had fallen out with my dad at the time and said she wouldn't come unless he didn't come. There was no question in my mind that my mum and dad would not be at my wedding.
To even think of having a wedding without your mum and dad but to have your brother and his girlfriend there is VVVVU.
To think of doing it without telling them - I don't even know how anyone with a heart could do such a thing.
It's not about forgiveness. When my dad found out that my sister had given me the ultimatum about my wedding it cut him to the core. The thought that he could have been cut out of the day would have made him so sad. He never let my sister know how hurt he was and he never would have told me either had I chosen to prioritise her over him.
To those who say that years down the line all you remember is the day - that just isn't true.
My dad is no longer with us and every time I look at the wedding pictures with him in them looking so proud it makes me so happy.
Parental love is unconditional. They will forgive you, of course they will. The hurt that you're going to inflict will live with them forever and if you are any kind of human being the knowledge that you inflicted that hurt will live with you too forever once they have gone.
Because they will go one day and then you won't have these sorts of dilemmas to deal with.
You're perfectly within your rights to invite your mum, dad and stepdad and put your foot down about the extended family. If that guest list is too much then knock a couple of friends off and tell your brother that his girlfriend can't come.
If your dad can't afford to go abroad why are having a wedding abroad in the first place? If you really have your heart set on getting married abroad why not postpone and give a year's notice so that he can save up to come?
I would be so hurt if my children did this to me, I would be forever wondering what I did to deserve it. The fact that you're brother is going and she is not being told - it's just beyond awful.
I don't know what else to say OP. You are right to feel guilty and I can't see how you can enjoy your day tbh.