I just wanted to say that throughout our wedding planning, we've had moments where parents are driving us a bit mad and that you're not alone. I don't know if its because we're not having the wedding my parents would like (we did initially forget that the wedding day is mine and my finances and his familys i.e. my family and I can't make all the decisions and expect my fiancé and his family to just say yes) or because they/my Mum didn't enjoy her own wedding day so she's worrying unnecessarily about this...I'm not sure but we have had guest list pain points shall we say!
My Mum wanted a small wedding which we did by cutting our friends out the civi ceremony then with my fiancés family having a handful of family / friends, we then had some non-negotiable family members my parents felt they "had to" invite and they know I have no relationship with my cousins but they had to be there...and at first, the cousins (15) were invited to the party only but then they suddenly had to be invited to the whole day...so we've ended up with 60 for the civil ceremony and then some for the meal and party - and we used to hear "You and H2B have made this into a big wedding". i'm not an argumentative person, I'm pretty relaxed so just let it slide (but yes - extremely frustrating!!).
That's been our main pain point (my Mum's a pretty anxious person and has various health problems too :-( so been tough to really let rip) but i kept reminding myself that the day is about me and H2B getting married, that's all that matters and if we end up having the world and his wife there then so be it/my parents can host/entertain them because me and H2B will be partying with our mates! I mean this in a positive way but its like water off a ducks back now when another couple's name pops up to be invited..meh. I'm a fairly relaxed person and not very girly so probably have a different view to the majority of brides to be but do you think you could explain to your parents how this is making you both feel, find out why/understand why your Dad won't have same suit etc. If, after explaining, they still want your sister to wear white, your Dad to not wear same suits - do you think you could reach a point of "OK fine, its one day, as long as me and my H2B get married, they can do what they want?" Appreciate that may be tough if you're someone who has planned every tiny detail. Hope that helps - in some way!? Good luck!