A while back I posted that if you are somehow descended from Patrick Grehan Senior (1756 -1832) and Judith Grehan (neé Moore), then you are a fourth cousin of Anne Boleyn , and a fifth cousin of Elizabeth 1st. You can find that post here. I hadn’t taken it any further, so I’m grateful to Nancy Beckley for pushing things back to Edward the First. I picked it up, and pushed it a bit further. It all seems very impressive until you do the maths. 27th great-grandparent means there are another 536 million other great-grandparents who aren’t kings or queens. Still it’s always nice having a saint in the family.
Saint Margaret is Scotland’s only royal saint, and Malcolm is the one in Macbeth.
27th great grandparents William the Conqueror (1028–1087) and Matilda of Flanders (1031-1083), and also Saint Margaret and the Scottish king Malcolm III.
26th great grandparents Henry I (1068 – 1135) and Matilda [originally christened Edith] of Scotland (c. 1080 – 1 May 1118),
25th great grandparents Geoffrey V (1113 – 1151) of Anjou and Matilda, (1102 – 1167)
24th great grandparents Henry II ( 1154 -1189) and Eleanor of Aquitaine (1122 -1204)
23rd great grandparents King John (1199-1216) Isabella of Angoulême (1188 – 1246)
22nd great grandparents Henry III (1207-1272)/Eleanor of Provence (1223 – 1291)
21st great grandparents: King Edward I (1239-1307)/Eleanor of Castile (1241 – 1290)
20th great grandparents: Elizabeth of Rhuddlan (1282-1316)./ Humphrey de Bohun, (1276-1322) 4th Earl of Hereford (second husband)
19th great grandparents: Lady Eleanor de Bohun (1304-1363)/James Butler (1305-1338), 1st Earl of Ormond
18th great grandparents: James Butler (1331-1382), 2nd Earl of Ormond/Elizabeth Darcy (1332-1390)
17th great grandparents: James Butler (1359-1405), 3rd Earl of Ormond/Anne Welles (1360 -1397)
16th great grandparents: Richard Butler (1395-1443), Sir Richard Butler of Polestown/ Catherine O’Reilly(1395-1420), Gildas O’Reilly, Lord of East Breifne
15th great grandparents: Edmund MacRichard Butler (1420-1464), The MacRichard of Ossory/ Catherine O’Carroll (?-1506)
14th great grandparents: Sir James Butler (1438 -1487),/Sabh Kavanagh (1440 -1508), Princess of Leinster, daughter of Donal Reagh Kavanagh MacMurrough, King of Leinster (1396-1476)
13th great grandparents: Piers Butler (1467-1539), 8th Earl of Ormond/Margaret Fitzgerald (c.1473 -1542)
12th great grandparents: Thomas Butler (?-1532)/wife not known
11th great grandparents: Margaret Butler/Rory O’More (?-1556)
10th great grandparents: Lewis O’More/wife not known
9th great grandparents: Walter Moore/Alicia Elliott
8th great grandparents: Patrick Moore/Joan O’Hely
7th great grandparents: Edmund Moore/Elizabeth Graham
6th great grandparents: James Moore (?-1741)/Mary Cullen
5th great grandparents: Edward Moore (?-1787)/Jane Reynolds
4th great grandparents: Judith Moore (1763-?)/Patrick Grehan (1758-1832)
3rd great grandparents: Patrick Grehan (1791-1853)/Harriet Lescher (1811-1877)
2nd great grandparents: Celia Mary Grehan(1838-1901)JohnRoche O’Bryen1810-1870
1st great grandparents: Ernest A O’Bryen 1865-1919/Gertrude Purssell 1873 -1950
Forgotten Victorians 
Impressive. And I like the maths bit , Will. I haven’t discovered much new recently as regards the relationship of our families but have come across a couple of Bellord references.
My 11th Great-grandparents were Ruari Coach O’ Mordha and Margaret of Ormonde Butler through his son Callagh O’ Mordha