In order to understand this nursery rhyme, "See Saw Sack-a-day", you need to know a little history about the British throne. The Dukes of Monmouth, Richmond and Grafton were all illegitimate sons of King Charles II. Charles II had no legitimate children. The "pious brother" was Charles' actual brother, who thus became King James II after Charles died.
Interestingly, this rhyme has some modern significance. Diana, the Princess of Wales descended from the Dukes of Grafton and Richmond. Prince William, Diana's son, is in line for the throne. If he becomes king one day, he'll be the first heir of King Charles II to become a monarch.
See saw, sack-a-day;
Monmouth is a pretty boy,
Richmond is another,
Grafton is my only joy,
And why should I these three destroy,
To please a pious brother!
Halliwell (a collector of nursery rhymes in the 19th century) wrote the following about this rhyme: "Taken from MS. Douce, 357, fol. 124. See Echard's 'History of England,' book iii, chap. 1." MS Douce was written circa 1642.
Photos & Illustrations
Thanks and Acknowledgements
This rhyme can be found in "The Nursery Rhymes of England" 5th edition (1886), collected by James Orchard Halliwell and illustrated by W. B. Scott.