MC (female) is getting engage to/ married into a family where some of the members have blood that can kill others that get in touch with it. Except the MC, who only either faints or come back to life after a little while.

Not all of the family members have this "curse".

The big sister of the male MC was married and had a child, but the child did not have that "cursed" blood. And unfortunaly died when he accidentaly tuched a place the mother had hurt herself on.

Never mind, found it.

It's called "My In-laws are Obsessed With Me".