1566:
April: Katherine Grey, age 26 , gives birth to a third son named Henry after her father Henry Grey
August: Mary Seymour, age 18, daughter of Thomas Seymour and Catherine Parr, marries Henry, age 21, Duke of Palatinate-Neuberg, after meeting and falling in love during one of Henry's visits to his English cousins
September: Elisabeth of Valois, Queen consort of England, age 21, gives birth to her second child and first daughter, named Jane after her late mother-in-law Jane Seymour
November: Anna of Austria, wife of Carlos, Prince of Asturias since 1563, gives birth to their first child, a daughter they name Maria Manuela after Carlo's deceased mother
December: Catherine of Palatinate-Neuberg, age 24, gives birth to her fourth child, a third daughter who she names Sibylle after her late mother-in-law, Sibylle of Cleves, sister of Anne of Cleves, the fourth wife of King Henry VIII
1567:
February: Mary, Queen of Scots, age 25, gives birth to her second son, named Alexander, a traditional name in the Scottish royal family
August: Diego Felix, Infante of Spain, dies after a long illness at the age of 4. His parents, King Felipe III and Barbara of Austria, are grief-stricken
1568:
January: Barbara of Austria, Queen consort of Spain, age 29, gives birth to her fifth child and third daughter, named Ana Sofia
March: Elisabeth of Valois, age 21, gives birth to her third child, another daughter, named Katherine. English subjects are disappointed, but King Edward is delighted to have another daughter, as he is very close to his first, who is nearly two years old
March: Anna of Austria, age 19, gives birth to her second child, a son named Felipe Prospero
August: Mary, Queen of Scots, age 26, gives birth to her third child, a daughter named Mary after herself
1570:
January: Anna of Austria, age 21, gives birth to her third child, another son named Carlos Felipe
January: Mary Seymour, Duchess consort of Palatinate-Neuberg, age 22, gives birth to her first child, a daughter named Mary after herself and her mother-in-law, Mary Tudor, age 54
1571:
August: Carlos Felipe, the second son of Prince Carlos of Asturias and Anna of Austria, dies at 1 year old of tuberculosis
1572:
June: Jeanne III, Queen of Navarre, age 43, dies of suspected poisoning by Catherine de Medici. Her son, Henri III, becomes King of Navarre at age 19, and his new bride, Marguerite of France, daughter of Catherine de Medici, becomes Queen consort
July: Anna of Austria, age 23, gives birth to her fourth child, a third son named Fernando Lorenzo
August: Elisabeth of Valois, age 27, gives birth to her fourth child, a son named Edmund. He is made Duke of York later in toddlerhood
September: Barbara of Austria, age 33, gives birth to her sixth child and third son, named Felipe Laurenco
September: Mary, Queen of Scots, age 30, gives birth to fourth child, a second daughter named Margaret, after her grandmother Margaret Tudor
October: Elisabeth of Austria, age 18, gives birth to a daughter, Marie-Elisabeth, after two years of marriage to King Charles IX of France, age 22
1573:
June: Elisabeth of Valois, age 28, gives birth to her fifth child, a daughter named Margaret
September: Mary Seymour, age 25, gives birth to her second child, another daughter named Catherine after her sister-in-law and grandmother-in-law, Catherine of Aragon
1574:
May: Edward Courtenay, eldest son of Elizabeth Tudor and Edward Courtenay the elder, marries Jane Dudley, the second daughter of Jane Grey and Guildford Dudley
1575:
March: Anne Courtenay, age 21, eldest daughter of Elizabeth Tudor and Edward Courtenay the elder, marries Francis Knollys the younger, age 23, fifth son of Catherine Carey and Francis Knollys the elder
April: Mary Seymour, age 27, gives birth to her third child, another daughter named Elizabeth
October: Anna of Austria, age 26, gives birth to her fifth child and second daughter, named Isabel Maria
1576:
May: Jane Dudley, age 19, gives birth to her first child, a daughter, Jane Courtenay, named after herself and her mother Jane Grey
July: Elisabeth of Valois, age 31, gives birth to her sixth child and third son, named Francis after her deceased brother, Francois II of France
September: Elizabeth Courtenay, third child of Elizabeth Tudor and Edward Courtenay the elder, age 18, marries Edmund Carey, also age 18, the fourth son of Henry Carey and Anne Morgan
1577:
March: Anne Courtenay, age 23, gives birth to her first child, a daughter, Elizabeth Knollys, named after her grandmother Elizabeth Tudor, age 44
May: Jane Dudley, age 20, gives birth to her second child, a son, Henry Courtenay
June: Mary, Queen of Scots, age 35, gives birth to her fifth child, a third daughter named Eleanor
July: Mary Seymour, age 29, gives birth to her fourth child, a son named Henry after her husband. She and her husband are relieved after the birth of three daughters
November: Anna of Austria, age 28, gives birth to her sixth child and fourth son, named Carlos Felipe, after her deceased son who died six years prior
1578:
August: Anne Courtenay, age 24, gives birth to her second child, another daughter, Catherine Knollys
1579:
February: Elizabeth Courtenay, age 21, gives birth to her first child, Elizabeth Carey, named after herself and her mother, Elizabeth Tudor
July: Anna of Austria, age 30, gives birth to her seventh child and third daughter, named Ana Constanza, after herself
July: Elisabeth of Austria, age 25, gives birth to her second child after seven years of no pregnancies, to a son named Francois Antoine
September: Jane Dudley, age 22, gives birth to her third child, William Courtenay
1580:
July: Carlos, Prince of Asturias, dies at the age of 35 after a long life of mental instability. His long-suffering wife is now left to care for their six surviving children. Their 12 year old son, Felipe Prospero, is now the Heir to the Kingdom of Spain
October: Fernando Lorenzo, fourth child of the late Prince of Asturias and Anna of Austria, dies at the age of 8 of pneumonia. His mother, Anna, is distraught at losing a child only three months after the death of her husband Carlos. Her stepmother-in-law (And paternal Aunt), Barbara of Austria, comforts her in her grief and brings her and her remaining five children to court, to assist her in raising them
October: Anne Courtenay, age 26, gives birth to her third daughter, Anne Knollys, named for herself and her grandmother/namesake, Anne Boleyn
November: Prince Francis of England, youngest son of Edward VI and Elisabeth of Valois, dies of tuberculosis at the age of 4. His parents bury their youngest solemnly and the Kingdom of England grieves for many years
Line of Succession in England as of the end of 1580:
1. Prince Edward, age 16
2. Prince Edmund, age 8
3. Princess Jane, age 14
4. Princess Katherine, age 12
5. Princess Margaret, age 7
6. Elizabeth Tudor, age 47
7. Edward Courtenay, age 24
8. Henry Courtenay, age 3
9. William Courtenay, age 1
10. Arthur Courtenay, age 16
11 Anne Courtenay, age 26
12. Elizabeth Courtenay, age 22
13. Catherine Courtenay, age 19
let me know if anything seems weird or if the line of succession doesn't make sense. I know typically it wouldn't go straight from Edmund to Princess Jane, however I feel that Edward VI would rather it go to his child, even a daughter, rather than a nephew/cousin, etc, hence I think his daughters would be included in the line of succession (He also has a nearly adult Heir , so its more likely that England go to a future grandson in the event of Prince Edward and Prince Edmund's deaths anyway). I also didn't include those past Catherine Courtenay because I didn't feel like it, but it would go to Jane Grey, then her sons, their sons, and then Jane's daughters and then their sons, etc, maybe going to Katherine Grey eventually, who has three sons (Who are Seymours), and the worst-case scenario it would eventually get to Mary, Queen of Scots (who, at this point, wouldn't be accepted as England is more used to a Protestant, Tudor monarch (Of course theres probably still Catholics who want Mary as their queen, though)