Were John Baptist and Jesus really related? If Jesus was of the tribe of Judah, with both his parents of the lineage of David, and John the Baptist's parents of Levi's tribe, Luke 1.5, how is it possible that John and Jesus could be related, Luke 1.36?
According to the Bible, Elizabeth (mother of John the Baptist) and Mary (mother of Jesus) were related.  Luke 1:5 says that Zechariah belonged to the priestly division of Abijah and his wife Elizabeth was also a descendant of Aaron.  Luke 1:36 says that Elizabeth was a relative of Mary.   Here is an extract from an article that explains how this is possible - https://www.gotquestions.org/Mary-lineage.html

An argument sometimes put forward by those who deny the credentials of Christ is that, if Mary was Elizabeth’s “cousin,” then Mary must also have been a Levite. Some translations, such as the KJV, do state that Mary was the “cousin” of Elizabeth (Luke 1:36). However, the English word cousin does not have to imply a close relation, and other versions of the Bible translate the word as “relative” (NKJV, NIV, ESV, CSB, BSB).


Even if Elizabeth and Mary were close relatives, it was still possible for them to be of different tribes, as women were identified with their father’s tribe, not their mother’s. Elizabeth’s father was a Levite, making her a Levite by birth, but her mother may have been of Judah. Conversely, Mary’s mother may have been a Levite and kin to Elizabeth’s family, while Mary’s father was of Judah. Luke’s genealogy shows that Heli, whom we assume to be Mary’s father, was a direct descendant of Judah, not Levi. In addition, the angel Gabriel affirmed Jesus’ Judean lineage, telling Mary that “he will be very great and will be called the Son of the Most High. The Lord God will give him the throne of his ancestor David” (Luke 1:32, NLT).  David was of the tribe of Judah.

The Bible does not say if Elizabeth was Mary’s cousin, aunt or other relation.  We do know, however, that Elizabeth was getting on in years when she became pregnant while Mary was a young woman.  Regardless of how Mary and Elizabeth were related, Jesus is a descendant of David and Judah:

Hebrews 7:14: For it is evident that our Lord was descended from Judah....


Revelation 5:5: And one of the elders said to me, “Weep no more; behold, the Lion of the tribe of Judah, the Root of David, has conquered, so that he can open the scroll and its seven seals.”