Can Margaret marry Henry II of Navarre (1503)?
nope. Not important enough.
Say both Catherine and Arthur survive their sickness unscathed, and go on to have many kids. Who would these alternate heirs marry, and how would it compare to our world and Henry's kids?
Alternate Issue;
1502, Elizabeth
1503, Mary
1504, Arthur
1506, Margaret
1507, Henry
1509, Edward
1510, Catherine
1511, Joan
1513, Edmund
1514, John
1516, Blanche
1518, Cecily
probably gonna be some of those dying in infancy. After all, five out of Katherine's six kids died in infancy or were stillborn OTL. Yes, the argument can be made that there were health problems caused by her excessive fastings etc, but that doesn't change the fact that infant mortality
was high and that you have her popping out a kid every year except 1505, 1508, 1512 and 1517. Poor woman's body needs a chance to recover.
My two cents:
Elizabeth to Karl V
Mary to Joao III
Arthur to Katharina of Austria
Margaret can die in infancy,
Catherine can be second wife of François I- find it difficult to believe that Arthur wouldn't still feel "miffed" by Karl V's high handed treatment.
Joan (I'd swap she and Margaret's names around, let her birth coincide with Philipp the Handsome and Juana la Loca being shipwrecked in England. Juana named her daughter Katherina as a result) maybe gets James V. Maybe. Depending on Anglo-Scots relations.
Blanche can take Hans of Denmark (son of Christian II) or Christian III
Cecily perhaps to François' son and heir?
For the younger boys
Henry, duke of Bedford maybe marries some second tier royal
Edward, duke of Clarence marries Anne Bourchier, Baroness Bourchier
Edmund, duke of Gloucester marries another Bourchier heiress, daughter of the earl of Bath or alternately, the only daughter of the earl of Arundel (who's brother dies in infancy)
John, duke of Rutland marries the daughter of Anne Sapcote and her half-de Vere Broughton first husband, gets the full portion of the Broughton inheritance after Anne's son dies in 1528 and pretty much most of the de Vere inheritance that the earl of Oxford had left to his bastard daughter, Broughton's mom. Another canddiate is Margaret Swynnerton, an heiress in Staffordshire.