IMO, when 2 people of different upbringing come together, sure have differences between each other.
when both side parents are involved, it will probably be worse.
for myself, i have different issues. eg. my mum is more loud and direct but generally nice but it was a shock to my WTB as her family don't talk loudly.
So last time got quite a bit of friction. when i raise my voice a bit to stress on certain points during our conversations, she will think i am scolding her and will cry. but now no more liao.
However my mum is still louder than me. Sometimes when she talks to my dad, my WTB also got shocked.
it takes a while to get comfortable with this.
Myself, i feel that if during courtship, both parties don't mix with each other folks, problems like this sure arise.
Especially these days, both parties are working and only have weekend to spend with each other. Weekends will be spent going out and if never do stayovers and don't understand how it's like to be with your future in-laws, sure get shell shocked one.
have to go with a more open mind and open heart bah. these are common problems for any couples settling down.
I also have issues with my future in laws and i straight away tell my WTB abt it. she is the one who knows them best, so she assured me some things and i take her assurance on it.
So talking and spending more time with them should help.