Brian Boru has many famous ancestors living today, here are a few:

Queen Elizabeth II

Apparently Brian Boru (Bryan Boru) is related to the Queen of England; Her majesty is a direct descent of Brian Boru, who is a 35th great-grandfather. 

This is the most direct line of descent from Brian Boru to the Queen of England Elizabeth II:

Brian Boru ---> Tadc ---> Toirdelbach ---> Muirchertach ---> Mor ---> Derbforgaill ---> Murchad ---> Donnchada ---> Enna ---> Diarmaid ---> Aoife ---> Isabel de Clare ---> Isabel Marshal ---> Isabella of Gloucester and Hertford ---> Robert, 6th Lord of Annandale ---> Robert I of Scotland ---> Marjorie ---> Robert II of Scotland ---> Robert III ---> James I ---> James II ---> James III ---> James IV ---> James V ---> Mary, Queen of Scots ---> James VI and I of Scotland and England ---> Elizabeth of Bohemia ---> Sophia of Hanover ---> George I ---> George II ---> Frederick, Prince of Wales --->  V ---> George VI ---> Queen Elizabeth II

John F Kennedy – 35th President of the United States

The Irish name Kennedy originated from Mac Cennétig (Kennedy) memebers of the Dál gCais.  The name Kennedy came from the old meaning “helmet head”. Coat of Arms of the Kennedy clan have three helmets on its shield.  They are descended from Dunchaun, who was the brother of the Great High King Brian Boru. In the 11th to the 15th centuries the Kennedys were Lords of Ormond.There are several versions of how the Kennedy's got started, but when one goes in and examines things, what turns out is that the origins of the Kennedy's to Ireland is very clear.

Ronald Regan – 40th President of the United States

The ancestral line of Ronald Regan can be traced back to Ireland in the early 1800s.  It is said, that his ancestors originated from the ancient Irish Clan namely the Munster O’Regan’s in County Limerick, Munster.  O’Regan is sometimes spelt Regan or Reagan. The O’Regan Clan from Munster is descended from Riacan (Riagan), who was a nephew of the famous Brian Boru.  The Dal gCais of Thomond are approximately 31st cousins twice removed to Ronald Regan.

Barack Obama – 44th and current President of the United States

The current President of the United States apparently has royal ties. Genealogists have traced Obama's roots back to British monarchs Edward I of England and William the Lion of Scotland.  It is said that he is a descendant of Brian Boru (Bryan Boru) High King who ruled Ireland from 1002 until 1014.

Duchess of Cambridge, Kate Middleton

There is research to verify that Kate Middleton has connections through the Lupton family from Yorkshire who are in turn contact to the noble Fitzmaurice family from Co Kerry.

Genealogists research show that the Duchess of Cambridge, who is married to Prince William, the Duke of Cambridge and 2nd in line to the throne of England, who also has connections to Brian Boru through his Grandmother the Queen of England, has connections through the Lupton family of Yorkshire, England with the Fitzmaurice’s who are a noble family hailing from County Kerry. The Fitzmaurice family from County Kerry have strong links to Brian Boru (Bryan Boru), High King of Ireland.

Prince William

Kate Middleton's husband, Prince William, who is 2nd in line to the Thone of England is in turn also related to Brian Boru (Bryan Boru) through his Grandmother the Queen of England, Queen Elizabeth II.