Luk 12:51 Suppose ye that I am come to give peace on earth? I tell you, Nay; but rather division:
Luk 12:52 For from henceforth there shall be five in one house divided, three against two, and two against three.
Luk 12:53 The father shall be divided against the son, and the son against the father; the mother against the daughter, and the daughter against the mother; the mother in law against her daughter in law, and the daughter in law against her mother in law.
Luk 12:54 And he said also to the people, When ye see a cloud rise out of the west, straightway ye say, There cometh a shower; and so it is.
Plain and simple that is the way it will be, but so be it, for Jesus had to bring salvation to the world, even though it would cause division between people, even family members.
Jesus wants peace on earth, and love thy neighbor as yourself, and follow peace with all men, with holiness, without which no person shall see the Lord.
But Jesus had to bring salvation to the world, and could not be avoided, so if it brings division among people, even dear family members, where they will fight with each other over whether it is true or not, then so be it, for Jesus had to bring salvation, and He was not going to abandon salvation because it would cause people to fight over whether it is true or not.
But it is like that with many things of the world that they fight among themselves over things, and the Bible already caused division among people, and the truth of it, before Jesus came to give salvation, but Jesus giving us salvation escalated the fighting among people more concerning God's word.
The Bible says children obey, and honor your parents, but children refusing to believe Jesus is the Savior of the world, and going against their parents who believe Jesus is the Savior, is not the children disobeying, and dishonoring their parents, and wives who believe, and husbands who do not, and husbands who believe, and the wife does not, does not mean they are not respecting each other, but they are only offending God if they do not agree to the truth.
So if they fight in a household of whether Jesus is salvation or not, has nothing to do with them disrespecting each other, but they are offending God if not in the truth, so they can still have peace with each other, but disagree on whether Jesus is salvation or not, or whether they believe the Bible or not, like they would disagree over what food they like, or what car they like, or anything else, although agreeing with the truth, and going against the truth, is a way more serious matter.
There will be fighting against the saints from the world, and some to a very high degree resulting in hurt, and loss of life, but I do not believe that when Jesus said there would be division among family members over whether Jesus is the Savior or not He is not speaking of a very serious fighting scenario, or of persecution, but speaking by words and disagreement, that does no harm to the individual in a physical manner.
Although it could result in a physical confrontation, although highly unlikely, with the exception of the beast kingdom, for they will not care about their family if they have taken the mark of the beast, for they will have the nature of a devil then for they cannot have salvation then, Jesus is mainly saying in family squabbles that does not result in anything serious, and not like the world that is not their family and friends that will come at them a whole lot harder at times.
This peace that is upset it would mostly be in a mild manner, maybe a little escalated, but not like dealing with the world concerning the truth or not, at least for the very most part, for it could result in them not talking to each other, but not wanting to persecute each other physically over their difference, for how many people in family's go against each other in a harsh way over a difference than the world, for a family member would be more tolerant with more love to let it slide compared to the world, for you can call your brother an idiot and most likely get away with it, but not so much in the world.
So this peace that is upset is not like the peace that is upset in the world over the difference of whether Jesus is the Savior or not, but mostly the peace being upset is on the part of the people that are against truth in the world, but some made the mistake in the past that called themselves Christians of evening out the odds and fighting back physically, which they were not supposed to do, for if there is any peace to be upset it should always be on the part of the world if the saint abides in the truth, for we are to follow peace regardless of how people act towards us, and we are supposed to know when to shut our mouth so it does not come to a non peaceful situation.