Question
Assalaamu alaykum, Shaykh. Is the belief that Allah has a son (as Christians claim) or a daughter (as the tribe of Quraysh believed) Shirk (associating partners with Allah) in Ruboobiyyah (Lordship) or Shirk in Asmaa wa Sifaat (Divine Names and Attributes)?

Answer
All perfect praise be to Allah, the Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad, sallallahu ‘alayhi wa sallam, is His slave and Messenger.

Believing that Allah, the Exalted, has a son involves Shirk in Asmaa wa Sifaat (Allah's Names and Attributes) and Shirk in Ruboobiyyah (Allah's Lordship), and it leads to Shirk in Uloohiyyah (the Servitude to Allah); thus incorporating the three categories of Shirk.

Shaykh Ibn ʻUthaymeen may Allaah have mercy upon him said, "Shirk means associating partners to Allah in His Ruboobiyyah or His Uloohiyyah or His Asmaa wa Sifaat. Shirk in Ruboobiyyah means believing that there is another creator of the universe beside Allah or believe in an assistant to Him in the creation ... Shirk in Asmaa wa Sifaat means believing that the created beings possess attributes similar to the divine Attributes of the Creator." [Fataawa ʻala Ad-Darb]

Dr. ʻAbdul-ʻAzeez ibn Muhammad Aal Abdul-Lateef said, "Shirk in Ruboobiyyah accompanies Shirk in Asmaa wa Sifaat and inevitably leads to Shirk Uloohiyyah..." [Inhiraafaat Al-Qubooriyyeen: Ad-Daa' wa Ad-Dawaa']

Allah knows best.

From Islamweb.net

Notes:

1. Worshipping/praying to others apart from Allah is Kufr.

2. Worshipping/praying to others with Allah is Kufr.

3. The belief that Allah has a son is Kufr as Allah is free from the human imperfection of siring. It is also a great negation of many Qur'anic verses that states that Allah is one, without partners, son, etc.

4. Allah is Al-Ahad, the One. The belief that Allah is three in one is Kufr.

https://www.google.com/amp/s/www.islamweb.net/amp/en/fatwa/358144/

May Allah strengthen our hearts more towards Islam.. Jazakumllahu kayran..