In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
As a new Muslim, you should treat your family with good manners. And you can share their happiness. You can also join their celebrations as long as they are free of religious rituals or unlawful practices.
Answering your question about celebrating Christmas with non-Muslim family, Dar Al-Ifta Al-Misriyyah, states:
The Beauty of Islam
Islam is the religion of peace, mercy, beneficence, and maintaining relations. One of the most important obligations upon Muslims in our age is to show the beauty of Islam and be its best representatives through their manners and relations.
Islam does not command you to distance yourself from your family or to hate and antagonize them. Rather, it commands you to treat them in the best manner.
There is a great difference between the divine injunction to abhor disbelief such that a Muslim may prefer to be thrown in fire to leaving Islam and between hating people and your family and antagonizing them for their disbelief.
Do Muslims Hate People?
Islam has never commanded its followers to hate people. But Islam commanded Muslims to love them because they are God’s creation. And because man is the creation of God, cursed is the one who destroys him. This is because God the Almighty created man with His own hands, breathed into him of His spirit and ordered the angels to prostrate before him.
For this reason, respecting man is an angelic characteristic. Consequently, God the Almighty commanded us to love people, maintain ties of kinship. God also commanded us to treat others kindly, adopt noble manners, speak good words, give friendly smiles and maintain good companionship.
It is through these means that Islam spread to the west and east and conquered the hearts of people before their lands. We, therefore, advise you to behave as you normally would and be yourself. This is because Islam wants you to keep up your good spirits that inspire happiness, optimism and hope in those around you.
Treat your family with good manners and do not make a phone call to congratulate them on the occasion of Christmas. But share their happiness and join their celebrations as long as they are free of religious rituals or unlawful practices.
There is no objection to celebrating Christmas with non-Muslim family. Islam is an open system; its followers believe in all of its prophets and messengers and love and exalt them.
They likewise treat the followers of those prophets and messengers well in compliance with the words of God. We read in the Quean : “And do not argue with the People of the Scripture except in a way that is best” (Al-Ankabut 29: 46)
What Do Muslims Believe About Jesus?
Prophet Muhammad (peace be upon him) said: “I am the nearest of all the people to Jesus, son of Mary, both in this world and in the hereafter; no prophet was sent between me and him.” (Muslim)
Every Muslim believes that Jesus is a prophet from among mankind who performed great miracles. His miracles include reviving the dead and healing the ill by the will of God the Almighty, not as a god or the son of God.The Ruling
Celebrating Christmas with Non-Muslim Family
Therefore, celebrating Christmas regardless of the Christian doctrine of the sonship of Jesus, is an aspect of faith. Rejoice with your family and eat with them and refrain from consuming pork and alcohol with tact and graciousness. Ignore those who want to ruin your relationship with your family in the name of Islam as Islam is innocent of all of this.
Almighty Allah knows best.