This Gospel message sounds weird to our ears. Msgr. James Watkins explains in this homily on the 20th Sunday in Ordinary Time what Jesus is trying to tell us in the Luke 12 Gospel, verses 49-53:

Jesus said to his disciples: ‘I have come to set the earth on fire, and how I wish it were already blazing! There is a baptism with which I must be baptized, and how great is my anguish until it is accomplished! Do you think that I have come to establish peace on the earth? No, I tell you, but rather division. From now on a household of five will be divided, three against two and two against three; a father will be divided against his son and a son against his father, a mother against her daughter and a daughter against her mother, a mother-in-law against her daughter-in-law and a daughter-in-law against her mother-in-law.’”